Adding Decimals
Which setup would make it easiest to correctly add 4.7 + 2.35?
A. Put 4.7 and 2.35 next to each other without changing anything.
B. Line up the decimal points and add a zero to 4.7 if needed.
C. Line up the numbers on the right side and ignore the decimal points.
D. Move both decimal points to the right.
B. Line up the decimal points and add a zero to 4.7 if needed.
When subtracting decimals, why is it helpful to add zeros to the end of a decimal?
For example:
5.2 → 5.20
A. It changes the value of the number.
B. It makes the number larger.
C. It helps keep the place values lined up.
D. It moves the decimal point.
C. It helps keep the place values lined up.
Which statement is true when multiplying decimals?
A. You line up the decimal points before multiplying.
B. You multiply as if they are whole numbers, then use the number of decimal places in the factors to place the decimal in the answer.
C. You always move the decimal to the left in the answer.
D. You always add the number of decimal places.
B. You multiply as if they are whole numbers, then use the number of decimal places in the factors to place the decimal in the answer.
A student is solving:
5 ÷ 0.4
They turn it into:
50 ÷ 4 = 12.5
Then they say, "I'm done."
Are they correct? Explain why or why not.
They are correct.
A student is multiplying:
2/3 × 4/5
How to find the answer?
A. 2 + 4 and 3 + 5
B. 2 × 4 for the numerator and 3 × 5 for the denominator
C. 2 × 5 for the numerator and 3 × 4 for the denominator
D. Add the numerators and multiply the denominators
B. 2 × 4 for the numerator and 3 × 5 for the denominator
6.45 + 2.8
9.25
8.5 − 3.27
5.23
4.6 × 0.7
3.22
Will 7.2 ÷ 0.9 be greater or less than 7.2? Why?
Greater, because the divisor is less than 1.
2/3 × 3/4
1/2
You have $12.50. Your friend gives you $4.75 more.
How much money do you have now?
$17.25
A water bottle holds 2.5 liters. You drink 0.85 liters.
How many liters are left?
1.65 liters
A pack of stickers costs $2.75. Zoë buys 4 packs.
How much does she spend?
$11
A 12.6-meter ribbon is cut into pieces that are each 0.9 meters long.
How many pieces can be made?
14 pieces
Reduce 12/18
2/3
14.638 + 7.95 + 0.7
23.288
Solve:
15.004 − 7.86
7.144
3.24 × 1.6
5.184
7 ÷ 4
1.75
5/6 × 3/10
1/4
Sofia found the sum
2.4+3.75
_______
3.99
She did not correctly line up the decimal points/place values.
6.13
A student says:
“I know 8.2 − 3.75 = 5.55 because I subtracted 8 − 3 and .20 − .75.”
What is wrong with the student's thinking?
A. You cannot subtract a decimal from a whole number.
B. The decimal points need to be lined up, and 0.20 is less than 0.75, so regrouping is needed.
C. You should always subtract the smaller decimal from the larger decimal first.
D. You should move both decimal points before subtracting.
B. The decimal points need to be lined up, and 0.20 is less than 0.75, so regrouping is needed.
Marcus solves:
2.4 × 0.3 = 7.2
He says, "I multiplied 24 × 3 and got 72, so my answer is 7.2."
What is Marcus forgetting?
He needs to account for the two total decimal places in the factors. The correct answer is 0.72.
Why can we move the decimal point when dividing by a decimal?
For example:
4.8 ÷ 0.6 → 48 ÷ 6
A. We are changing only the divisor, so the quotient gets easier to find.
B. We are multiplying both numbers by 10, which keeps the value of the quotient the same.
C. Moving a decimal point always makes a number 10 times smaller.
D. We move the decimal because decimals cannot be divided.
B. We are multiplying both numbers by 10, which keeps the value of the quotient the same.
How do you change a mixed fraction into an improper fraction?
Multiply the whole number × denominator, then add the numerator