Percentages By Teacher Gel

MEANING OF PERCENTAGE Percentage is a fraction with 100 as its denominator. Percent means per 100. % is the symbol used to represent percent.

Example 1.) 60% of the students in this school are girls. Meaning: It means that in 100 students in the school, 60 of them are girls.

2.) Consumers must pay a tax of 7% of the total price. Meaning: It means that if a consumer buys 100 Baht worth of products, he has to pay 7 Baht as a tax.

3.) Nut scores 85% in a Mathematics Test.

Expressing decimals and fractions as percentages

PERCENTAGE (Per One hundred)

20/100 = 0.2 = 20%

RULE OF THREE Rule of Three is a method of finding the fourth term of a mathematical proportion when the first three terms are known.

Example 1 A dozen T- shirts cost 640 Baht. What is the cost of 3 T- shirts?

Working A: Let Working A: Let C 1 = first cost = 640 Baht N 1 = first number = 12 T- shirts C1C1 N2N2 C2C2 N1N1 = 160 Baht = 12 T shirts C2C2 = C1C1 N1N1 N2N2 = (640 Baht)(3 T shirts) C 2 = second cost = ? N 2 = Second number = 3 T- shirts Equation 1 4

Working B: Cost of 12 T-shirts = 640 Baht, Cost of 1 T-shirt = 640/12 Baht. Cost of 3 T-shirts = (3)(640/12) Baht = 160 Baht.

B. Answer The cost of three T-shirts is 160 Baht.

Example 2 Maya baked 425 cookies. 44% of the cookies were butter cookies. How many butter cookies did Maya bake?

Working A: If Maya baked 100 cookies, she would have 44 butter cookies. If Maya baked 1 cookie, should have 44/100 butter cookies. Since Maya baked 425 cookies, she had (425)(44/100) = 187 butter cookies.

Working B: In 100 baked cookies = 44 butter cookies. In 1 cookie = 44/100 butter cookies. In 425 cookies = (425)(44/100) butter cookies = 187 butter cookies. Answer: Maya baked 187 butter cookies.

Answer: Maya baked 187 butter cookies.

If 4 apples cost 52 Baht, how much do 12 apples cost? Special Seatwork ( 8 points)

Jack takes 35 minutes to read 100 pages. How long does he take to read 420 pages? Special Seatwork ( 8 points)

FINDING THE VALUE OF THE PERCENTAGE OF A QUANTITY Rule: To find the value of the percentage of the quantity, firstly convert the percentage into a fraction or decimal. Then, multiply it to the quantity.

Example 1.) What is 20% of 600? A. Solution: 20% of 600 = 0.2 x 600 = 120 or 20% of 600 = 20/100 x 600 = 120 B. Answer The 20% of 600 is 120.

2.) Find the 79% of 200 grams. A. Solution: 79% of 200 grams= 0.79x200 grams = 158 grams B. Answer The 79% of 200 grams is 158 grams.

Calculate each of the following, 1.) 9 % of ) 33% of ) 125% of 1,500 grams. 4.) 25% of ) 160% of 3,200 visitors

Problem Solving with percentage

Example 1.) 15% of Mother’s monthly salary goes towards paying the house rental. If Mother receives a monthly salary of 7,500 Baht, how much is the house rental per month?

A. Given 1. Mother receives a monthly salary of 7,500 Baht. 2. She pays 15% of her salary as the house rental. B. Required The amount of the monthly house rental.

C. Solution Let MHS = Monthly house rental Then, MHS = 15% of 7,500 Baht = 15/100 x 7,500 Baht = 1,125 baht D. Answer The house rental is 1,125 Baht per month.

FINDING THE PERCENTAGE OF A NUMBER OUT OF THE ANOTHER NUMBER

Rule: To find the percentage of a number out of the another number, Write the first number as the numerator and the second number as the denominator of the fraction, then multiply by 100%

Example 1.) Write 6 out of 40 as a percentage A. Solution: 6 out of 40 = 6/40 x 100% = 15% B. Answer 6 out of 40 is the same as 15%

2.) Express 24 minutes out of 1 hour in percentage. A. Solution: 24 minutes out of 1 hour = 24 minutes out of 60 minutes = 24/60 x 100% = 40% B. Answer 24 minutes is 40% of 1 hour

Problem Solving with the percentage of a number out of another number

Example 1.) The sales tax on a 140-Baht bag is 9.8 Baht. Find the rate of the sales tax in percentage. A. Solution Rate of sales Tax = 9.8 Baht out of 140 Baht = 9.8/140 x 100% = 7 % B. Answer The rate of sales tax is 7 %.

Problem Solving Related to Singular Trading

PROFIT, LOSS, DISCOUNT AND SELLING PRICE

Equations/Formulas 1. Profit = Selling Price – Cost Price P = S – C 2. Loss = Cost Price – Selling price L = C – S 3. Discount = Tagged Price – Sold Price D = T - S 4. Selling price = Marked price – Discount S = M - D

Example 1. Ploy bought a shirt for 150 Baht and sold it for 230 Baht. How much profit or loss did Ploy make? A. Given Selling = 230 Baht. Cost price = 150 Baht.

B. Required : Profit C. Solution P = S – C = 230 Baht – 150 Baht P = 80 Baht D. Answer The profit that Ploy make in selling the shirt is 80 Baht.

2. Veena sold some pottery for 3,390 Baht and made a 13% profit. How much had Veena paid for the pottery?

3. June sells a pair of jeans for 900 Baht and incures a 20% loss. How much has June purchased the jeans for?

Finding the Percentage of Profit, Loss and Discount 1. Percentage of Profit = Profit / Cost Price x 100% 2. Percentage of Loss = Loss / Cost Price x 100% 3. Percentage of Discount = Discount / Tagged Price x 100%

Example 1. A shirt that cost 480 Baht is sold for 600 Baht. Find the percentage of the profit earned.

A. Given Cost price = 480 Baht. Selling price = 600 Baht. B. Required Percentage of profit

C. Solution Percentage of profit = (P/C)(100%) = S – C (100%) C = 600 – 480 (100%) 480 = 25% D. Answer The percentage of the profit earned is 25%.

Problem Solving Related to Multiple Trading

Example 1. Mother purchased a table for 1,450 Baht. Then she sold it and made a 15% profit. How much did Mother sell the table for?

A. Given 1. The cost of the purchased table is 1,450 Baht. 2. The rate of profit is 15 %. B. Required 1. The selling price of the table.

C. Solution Let S = Selling Price C = Cost Price R = Rate of Profit = 15% of 1,450 So, S = C + R =1, % of 1,450 =1, = 1, Baht C. Solution Let S = Selling Price C = Cost Price R = Rate of Profit = 15% of 1,450 So, S = C + R =1, % of 1,450 =1, = 1, Baht

D. Answer The mother sells the table for 1, Baht.

SIMPLE INTEREST Simple Interest – Interest calculated based from the original principal. Principal – The sum of money or the wealth in the form of money owned by the person.

SIMPLE INTEREST Simple Interest for one year = Rate per annum x Principal Simple interest for one month = Rate per annum x Principal 12 Simple interest for one day = Rate per annum x Principal 365

Simple Interest for one Year = Rate per annum x Principal Example 1. A bank pays an interest of 3.5% per annum. If Paul keeps 25,000 Baht in the bank for a year, how much interest will he earn?

A. Workings Simple Interest for a year = Rate per annum x Principal = 3.5% x 25,000 Baht = 875 Baht B. Answer Paul will earn an interest of 875 Baht.

VOCABULARY AND SPELLING TEST + LESSON 13 TEST