Construction Math Section 2: Whole numbers

What is a whole number? Complete units without fractions or decimals.

Digits and place value 5,316,247

Positive and negative numbers Positive numbers are greater than zero Negative numbers are less than zero ZERO Neither negative nor positive

Adding and Subtracting Sum Difference

Sum and word problems Different key words in word problems to indicate addition ◦ Total ◦ Sum ◦ Together ◦ Altogether ◦ Combine

Difference and Word Problems Different key words in word problems to indicate subtraction ◦ Minus ◦ Difference ◦ How much less ◦ How much more ◦ Amount of decrease ◦ Amount of increase ◦ How much is left

Test your skill In calculating a bid for a roof restoration, the contractor estimates that he will need $847 for lumber, $456 for roofing shingles and $169 for hardware. What is his total cost? What operator (+,-,*,/) do you need? Addition— “total” $1,472

Test your skill A plumbing contractor allotted $4,265 in his bank account to complete three residential jobs. If he estimates Job 1 to cost $1032, Job 2 to cost $943, and Job 3 to cost $1,341, how much money will he have left in the account for unexpected change orders? What operator (+,-,*,/) will we use? Subtraction– “have left” $949

Profit, the bottom line If we are looking to make a profit, we must make sure that the cost of labor and parts is not more than the amount we charge. Therefore, it is vitally important to be able to estimate and calculate cost versus amount of money available

Multiplying and dividing Product Quotient

Product 24 x 16

Quotient When dividing whole numbers, often they do not divide evenly. The left over part is called the remainder. Why is remainder important? Useful for calculating supplies. If I need 45 feet of rope and I have a selection of 30 foot sections, I can divide and find that I need 1.5 (or 1 and a remainder of 15) sections of rope. One section is not going to cut it, I’m going to need 2 sections. When looking at supplies, I must round up, no matter my remainder.

Quotient

Multiplication and Word Problems Look for key words to indicate the appropriate operation ◦ Product ◦ Times ◦ When given a single quantity—determine multiple quantities

Division and Word Problems Key words… do we detect the pattern here? KEY WORDS KEY WORDS KEY WORDS ◦ Quotient ◦ Divide ◦ For 1 ◦ For each ◦ Separate ◦ Per ◦ A ◦ When given multiple quantities—determine single quantity

Supplies Relationship

Test your skill Your supervisor sends you to the truck for 180 feet of electrical wire. When you get there, you find that the coils of wire come in 15ft lengths. How many coils of wire will you need to bring back? What operator (+,-,*,/) will you use? Division 180/15=12

Test your skill, follow up You get back to your supervisor and he tells you that for the next job, you will need 200 ft of the same wire that comes in 15 ft coils. How many coils will you need? 200/15= ◦ It is impossible to simply take coils back. ◦ When purchasing and calculating supplies, we must always round up to the nearest whole number. ◦ You will need to take back 14 coils in order to get the job done

Test your skill A crane rental company charges $383 per day, $1,224 a week (5 day week), and $3,381 a month. How much would it cost to rent the crane for 3 days? ◦ $1,149 (3x383) [3 x daily] 12 days? ◦ $4,596 (12 x 383) [12 x daily rate] ◦ $3,214 ((2 x 1,224) + (2 x 383) [(2 x weekly)+(2 x daily)]

That pesky crane again A crane rental company charges $383 per day, $1,224 a week (5 day week), and $3,381 a month. How much would it cost to rent the crane for 17 days? ◦ $6,511 (17 x 383) [17 x daily rate] ◦ $4,438 ((3 x 1,224) + (2 x 383)) [(3 x weekly) + (2 x daily) ◦ $3,381 (1 x 3,381) [1 x monthly]

Perimeter The distance around the outside of any closed shape, such as a rectangle, circle, or square Measure all sides and add them together 4m 1m P= =10

Perimeter of irregular figures Houses are not square boxes. 40 ft 20 ft 25 ft P= =160