Estimating and Calculating with Decimals

What error did the student make when calculating the total cost of the ribbon?

• They multiplied incorrectly.

• They added an extra zero to the product.

• They incorrectly placed the decimal point.

• They used the wrong operation.

What is the actual cost of the ribbon?

• $7.35

• $73.50

• $735.00

• $7,350.00

How many cups of food will Milo need for the entire trip?

• 15.145 cups

• 151.45 cups

• 1.5145 cups

• 1514.5 cups

Mia is bringing a bag containing 20 cups of dog food. Will this be enough for Milo's trip?

• No, because Milo needs 20 cups and Mia only has 15.145 cups.

• Yes, because Milo needs 15.145 cups and Mia has 20 cups.

• No, because Milo needs 15.145 cups and Mia only has 14 cups.

• Yes, because Milo needs 20 cups and Mia has 20 cups.

Are you enjoying the video lesson?

• Yes

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What is a quick estimation method to check if an answer for multiplying decimals is reasonable?

• Multiply the numbers as if they were whole numbers and then divide by 10.

• Round each factor to the nearest whole number and then multiply.

• Subtract the smaller factor from the larger factor.

• Add the two factors together.

What was Kara's error in calculating the total cost of lunch for 3 people at $6.75 each, if she got $18.25?

• She incorrectly rounded the numbers before multiplying.

• She forgot to add the regrouped number after multiplying the whole numbers.

• She placed the decimal point in the wrong position.

• She made a mistake in the initial multiplication of 3 x 5.

A teacher buys 4.2 meters of ribbon at $1.75 per meter. A student calculated the total cost as $7,350. What was the student's primary error?

• Incorrectly multiplying 175 by 42.

• Forgetting to place the decimal point in the product.

• Rounding the numbers before multiplication.

• Adding the numbers instead of multiplying.

Which of the following is a valid strategy for checking the reasonableness of an answer when multiplying decimals?

• Only checking the decimal placement.

• Only using estimation.

• Using estimation or checking the decimal placement.

• Ignoring both estimation and decimal placement.