Question for 18 and 22.

18. An package of 500 sheets of paper has a measured height of 51.5 mm.

Question: A) Estimate the thickness of a sheet of paper.

Answer: I estimate that the thickness of a sheet of paper is 0.1 mm.

Question:B) Is the actual thickness of a sheet of paper greater or less than your estimate?

how you know.

Answer: The actual thickness of a sheet of paper is greater the estimated one.Because i rounded 51.5 to 52

22) kyle entered in a snowmobile race.He has to do 5 laps on a 6.37-km course.His time for each lap is 1.35 min, 1.27 min,1.23 min, and 1.22 min.

Question: A) How long does it take him to do 5 laps?

Answer: It take 6.49 mins to finish 5 laps.

Question: B) What is his average speed? Round your answer to the neareast hundreth.

Answer: His average speed is 1.29.

Dividing Decimal Numbers

Question # 4 a) in your textbook : Without using a calculator, place the decimal point in the correct position. Show your thinking.

36.72 ÷ 30 = 1224

Showing my thinking: Use front end estimation. ( taking the first digit)

Step 1: 36.72 will turn into 30.

Step 2: 30 will stay the same. So it will be 30 ÷ 30, 30÷30 = 1

Step 3: Now you know that the answer be approximately 1

Answer: 36.72 ÷ 30 = 1.224

Question # 6 b) in your textbook: Estimate then calculate the answer.

4.56 ÷ 0.8 = ______

Estimation:

Step 1: Round 4.56 to the nearest whole number, which is 5.

Step 2: Change 0.8 to 0.5

Step 3: 5 ÷ 0.5 = 10

Answer: 4.56 ÷ 0.8 = 5.7

Question # 12 in your textbook: A contractor charged $398.75 to move the gravel for a garden. The contractor charges $72.50 per hour. How long did she work? Estimate, then calculate the answer.

Estimation:

Step 1 : Change $ 398.75 to $350.00

Step 2 : Change $ 72.50 into $ 70.00

Step 3 : 350 ÷ 70 = 5. That means the contractor worked for about 5 hours.

Answer: 398.75 ÷ 72.50 = 5.5 , the contractor worked for 5 and half hours.

If you need help on multiplication check this link out.