1. Teacher Guide
This lesson is designed to teach kids to ask a critical thinking question that you can’t just put into a search box to solve. To do that, we encourage them with smaller questions that search can help them answer. Make sure that you read the notes for each slide: they not only give you teaching tips but also provide answers and hints so you can help the kids if they are having trouble.
Remember, you can always send feedback to the Bing in the Classroom team at You can learn more about the program at bing.com/classroom and follow the daily lessons on our Partners In Learning site.
Want to extend today’s lesson? Consider using Skype in the Classroom to arrange for your class to chat with another class in today’s location. And if you are using Windows 8, you can also use the Bing apps to learn more about this location and topic; the Travel and News apps in particular make great teaching tools.
Nell Bang-Jensen is a teacher and theater artist living in Philadelphia, PA. Her passion for arts education has led her to a variety of roles including developing curriculum for Philadelphia Young Playwrights and teaching at numerous theaters and schools around the city. She works with playwrights from ages four to ninety on developing new work and is especially interested in alternative literacies and theater for social change. A graduate of Swarthmore College, she currently works in the Artistic Department of the Wilma Theater and, in addition to teaching, is a freelance actor and dramaturg. In 2011, Nell was named a Thomas J. Watson Fellow and spent her fellowship year traveling to seven countries studying how people get their names.
This lesson is designed to teach the Common Core State Standard: Measurement & Data
CCSS.Math.Content.3.MD.C.5 Recognize area as an attribute of plane figures and understand concepts of area measurement.
CCSS.Math.Content.3.MD.C.5.a A square with side length 1 unit, called "a unit square," is said to have "one square unit" of area, and can be used to measure area.
CCSS.Math.Content.3.MD.C.5.b A plane figure which can be covered without gaps or overlaps by n unit squares is said to have an area of n square units.
CCSS.Math.Content.3.MD.C.7.b Multiply side lengths to find areas of rectangles with whole-number side lengths in the context of solving real world and mathematical problems, and represent whole-number products as rectangular areas in mathematical reasoning.

2. What is the area of Son Doong Cave and why is this a useful measurement for comparing its size with other caves around the world?
© Carsten Peter/Getty Images
Having this up as kids come in is a great settle down activity. You can start class by asking them for thoughts about the picture or about ideas on how they could solve the question of the day.

3. What is the area of Son Doong Cave and why is this a useful measurement for comparing its size with other caves around the world?
There are several notable caves in Phong Nha-Kẻ Bàng National Park in Vietnam. But just five years ago, the world learned of the park’s Son Doong Cave, which is now considered the largest known cave on Earth. Aside from its immense size, Son Doong contains other unique features as well, including a forest inside the cave, a rushing river, and these limestone cave pearls.
Cave pearls form when fast-moving water pulls calcite from the surrounding stone, depositing it around a grain of sand. As more water flows past, the calcite layer grows and coats the sand evenly, making a spherical shape. Some cave pearls can even take on a white gloss similar to the pearls that form inside mollusks.
Depending on time, you can either have students read this silently to themselves, have one of them read out loud, or read it out loud yourself.

4. What is the area of Son Doong Cave and why is this a useful measurement for comparing its size with other caves around the world? 1
Web Search
Look online for a way of finding the area of a space using a formula. What is the formula and what does each letter in it represent? 2
Look online for a way of finding the area of a space by counting square units. Would this work as a way of finding the area of the Son Doong Cave? Why or why not? 3
How big is Son Doong Cave? What do you notice about how its size is described? 4
What unit will your answer be in? What does this unit represent? 5
Thinking
Why might area be a better way of measuring the size of a cave instead of just length or width? What does the area of a space tell us?
There are a couple of ways to use this slide, depending on how much technology you have in your classroom. You can have students find answers on their own, divide them into teams to have them do all the questions competitively, or have each team find the answer to a different question and then come back together. If you’re doing teams, it is often wise to assign them roles (one person typing, one person who is in charge of sharing back the answer, etc.)

5. What is the area of Son Doong Cave and why is this a useful measurement for comparing its size with other caves around the world? 5
Minutes
You can adjust this based on how much time you want to give kids. If a group isn’t able to answer in 5 minutes, you can give them the opportunity to update at the end of class or extend time.

6. What is the area of Son Doong Cave and why is this a useful measurement for comparing its size with other caves around the world? 1
Web Search
Look online for a way of finding the area of a space using a formula. What is the formula and what does each letter in it represent? 2
Look online for a way of finding the area of a space by counting square units. Would this work as a way of finding the area of the Son Doong Cave? Why or why not? 3
How big is Son Doong Cave? What do you notice about how its size is described? 4
What unit will your answer be in? What does this unit represent? 5
Thinking
Why might area be a better way of measuring the size of a cave instead of just length or width? What does the area of a space tell us?
You can ask the students verbally or let one of them come up and insert the answer or show how they got it. This way, you also have a record that you can keep as a class and share with parents, others.

7. What is the area of Son Doong Cave and why is this a useful measurement for comparing its size with other caves around the world? 1
Web Search
Look online for a way of finding the area of a space using a formula. What is the formula and what does each letter in it represent?
(Possible queries: “for kids, how to find the area of a space”, “for kids, finding the area of a room”, “for kids, formula to find area”).
From
The "area" of a room is the size of the floor. Suppose you wanted to find out whether your room was really bigger than your brother's room. You'll need to measure your room, and his room. Suppose your room is ten feet long and fifteen feet wide, but his room is eleven feet long and fourteen feet wide. Yours is wider, but his is longer. How can you tell which is really the biggest room? You find the area by multiplying the length (how long it is) by the width (how wide it is). Your room is 10 x 15 = 150 square feet. Your brother's room is 11 x 14 = 154 square feet. Ha! Just as you always suspected, his room is bigger. How unfair!
Students should learn from this description that the formula to find the area of a space is length x width. They should understand that this is sometimes represented with letters as : l x w = a (length x width = area).

8. What is the area of Son Doong Cave and why is this a useful measurement for comparing its size with other caves around the world? 2
Web Search
Look online for a way of finding the area of a space by counting square units. Would this work as a way of finding the area of the Son Doong Cave? Why or why not?
(Possible queries: “for kids, finding the area, counting unit squares”, “for kids, how to count unit squares find area”).
From
(See accompanying image on website). This square is 4 units long on each side. The surface area is the number of square units that fit into the square. As shown in the picture, the surface area of this square is 16 total square units.
With a rectangle and square we can also get the surface area by multiplying width (W) x length (L). Let's try that and see if we get the same answer: Area = W x L Area = 4 x 4 Area = 16 Hey, that's the same answer! Note: if the units were feet for this problem, the answer would be 16 feet squared. Not just 16 feet. When we give the answer for surface area we used squared to indicate that it's a surface area and not just a straight line.
Students should think about these two different methods (counting unit squares and using a formula) and think about what might be more appropriate for the Son Doong Cave. They should conclude that in a real-life example, such as a cave, unit squares wouldn’t be marked out. Instead, it would make more sense to measure the length and the width in a specific unit (like feet, inches, meters, etc…) and solve using the formula.

9. What is the area of Son Doong Cave and why is this a useful measurement for comparing its size with other caves around the world? 3
Web Search
How big is Son Doong Cave? What do you notice about how its size is described?
(Possible queries: “how big is Son Doong Cave?”, “size of Son Doong Cave”).
From
Measuring more than 650 ft. high and almost 500 ft. wide, Hang Son Doong (Mountain River Cave) is believed to be almost twice the size of the current record holder.
Students should note that the cave’s size is described in terms of width and height and its measurements are given in feet.

10. What is the area of Son Doong Cave and why is this a useful measurement for comparing its size with other caves around the world? 4
Web Search
What unit will your answer be in? What does this unit represent?
(Possible queries: “unit used to describe area”, “what units to use when finding area”, “finding area, what do square units mean?”).
From and
There are many units used to describe area. Most start with the word 'square' e.g. 'square feet', 'square metres'. To get the amount of space inside a figure, we use a square to represent 1 unit and we say that the area is measured in square units. Take a look at the following rectangle. To get the area, we are going to draw squares of equal sizes inside of it. (See image on website). 1 square represents 1 square unit. The rectangle has 8 squares, so the area for this rectangle is 8 square units. We can also write 8 units2 and it will mean the same.
In practice, when looking for the area of shapes, you will be using real life units such, inches, yards, feet, and so forth. The following examples demonstrate how to do this (See second image on website). Notice here the unit we are using is inch. That means we are going to use squares, which have a side of 1 inch to get the area for the rectangle. Area = length × width = 5 × 2 = 10 square inches or 10 inches2. This also means that we can fit 10 squares with a side of 1 inch inside this rectangle.

11. What is the area of Son Doong Cave and why is this a useful measurement for comparing its size with other caves around the world? 5
Thinking
Why might area be a better way of measuring the size of a cave instead of just length or width? What does the area of a space tell us?
Students should think about what the area of a cave tells us as opposed to just measuring length or width. They should think about how another cave in the world may be longer or wider, but the area tells us what the overall size is. In other words, area is a way of telling us how much space is inside the cave, rather than just how long or tall it is. If it helps for them to compare different ways the sizes of caves might be evaluated in contrast to finding the area, they can search for other caves in the world who are thought to be the longest or widest. (Possible queries: “longest cave in the world”, “tallest cave in the world”) and may notice they get different answers besides the Son Doong Cave.

12. What is the area of Son Doong Cave and why is this a useful measurement for comparing its size with other caves around the world?
This slide is a chance to summarize the information from the previous slides to build your final answer to the question. Students should use the formula they have found to find the area of the Son Doong Cave.
Length: 650 feet
Width: 500 feet
650 feet x 500 feet = 325,000 square feet.
Students should be sure to give their answer in square feet. They should also be able to give an overview of why area may be a useful way of comparing sizes of caves around the world. Area describes the entire space inside the cave, as opposed to just its length, height, or width.