Dividing Decimals: Homework

Move the point in the divisor until it is a whole number, move the dividend's point the same distance, then divide.

Part A — Divide / 10

Write the quotient. Check each one by multiplying back.

1.
8.4 ÷ 2Answer
2.
0.96 ÷ 4Answer
3.
7.5 ÷ 0.5Answer
4.
3.6 ÷ 0.09Answer
5.
12.6 ÷ 0.7Answer
6.
0.288 ÷ 0.12Answer
7.
45 ÷ 1.5Answer
8.
0.5 ÷ 0.8Answer
9.
2.07 ÷ 0.09Answer
10.
18.9 ÷ 0.003Answer

Part B — Don't Get Fooled / 5

Each of these has a trap. Estimate first so you know about how big the answer should be.

1.
0.6 ÷ 3. Is the answer 2 or 0.2?Answer
2.
2.4 ÷ 0.6. A student divides the small number into the big one wrong and gets 0.4. What is the real answer?Answer
3.
6 ÷ 0.25. Will the quotient be more or less than 6? Find it.Answer
4.
A student says 15.5 ÷ 0.5 = 3.1. Dividing by a number less than 1 gives a bigger answer than 15.5. What is the real answer?Answer
5.
0.9 ÷ 0.003. Keep the zeros that hold the place.Answer

Part C — Metals and Money / 6

Real numbers. Density is how much a cubic centimeter weighs, so volume equals mass divided by density. The masses are made up; the densities and coin weights are real.

1.
Density, in grams per cubic centimeter:
Metal Density
Aluminum 2.7
Iron 7.87
Gold 19.32
a. A block of aluminum has a mass of 54 grams. What is its volume in cubic centimeters?Answer
b. A piece of iron has a mass of 157.4 grams. What is its volume?Answer
c. A gold nugget has a mass of 96.6 grams. What is its volume?Answer
2.
How much each coin weighs, in grams:
Coin Grams
Nickel 5.000
Dime 2.268
Quarter 5.670
a. How many dimes weigh 45.36 grams?Answer
b. How many quarters weigh 283.5 grams?Answer
c. One pound is about 453.6 grams. How many dimes weigh a pound? How much money is that?Answer

Metal	Density
Aluminum	2.7
Iron	7.87
Gold	19.32

Coin	Grams
Nickel	5.000
Dime	2.268
Quarter	5.670

Part D — Critical Thinking / 2

Think it through, then write your answer and one sentence about how you knew.

1.
Place decimal points in 756 and 18 so that 756 ÷ 18 = 4.2.Answer
2.
Dividing by a number less than 1 makes the answer bigger. Explain it using 1.2 ÷ 0.15, and give the answer.Answer

Part E — Make Up a Problem / 1

Write your own, then work it.

1.
Write a division with a decimal divisor whose quotient is exactly 40. Check it by multiplying back.Answer

Total / 24

Graded by

Notes

Answer key

Part A — the quotients.

4.2
0.24
15
40
18
2.4
30
0.625
23
6,300

Part B — the answer.

0.2. 6 tenths divided by 3 is 2 tenths.
4. 0.6 fits into 2.4 four times, and 4 × 0.6 = 2.4.
24. Dividing by less than 1 makes the answer BIGGER, because 0.25 fits into 6 twenty-four times.
31. 0.5 fits into 15.5 thirty-one times.
300

Part C — the answers.

a. 20 cubic centimeters b. 20 cubic centimeters c. 5 cubic centimeters
a. 20 dimes b. 50 quarters c. 200 dimes, which is $20.00

Part D — one correct answer, and what a good explanation says.

One way: 7.56 ÷ 1.8 = 4.2, because 1.8 × 4.2 = 7.56. Another is 0.756 ÷ 0.18 = 4.2.
8. The question asks how many 0.15s fit in 1.2. Each piece is small, so many fit. 8 × 0.15 = 1.2.

Part E — what a good problem looks like.

Answers vary. A good one checks, such as 3.2 ÷ 0.08 = 40, because 0.08 × 40 = 3.2.