Add and Subtract Decimals with Rounding and Estimation

Estimating is to....

• find the exact answer

• find something close to the correct answer

• use an algorithm

Compatible numbers are pairs of numbers that are easy to add, subtract, multiply, or divide mentally. When using estimation to approximate a calculation, replace actual numbers with compatible numbers.

• False

• True

a method for estimating a group of numbers by slightly adjusting some or all of the numbers to allow for easy mental computation

• factor

• fluency

• compatible numbers

• estimation

a method for estimating a number in which the first digit of a number is retained and all remaining digits are changed to zero

• fluency

• factor

• front-end method

• false

Which of the following is 9.029 rounded to the nearest hundredth?

• 9.0

• 9.02

• 9.03

• 9.029

Round 47.941 to the nearest tenth.

• 47.9

• 48

• 47.91

• 48.1

The total cost of a trip is $1067.50. The class has raised $819.24. How much more do they need?

• $1886.74

• $248.26

• $250.00

• $712.49

Richard needs 10.5 kg of flour. He has 5.17 kg in one bag and 5.2 kg in another. Does Richard have enough flour?

• Yes, he does

• No, he does not

How would you rate your comfort level with adding and subtracting decimals?

• I totally understand - I am super confident

• I am able to do most questions, but word problems confuse me

• I only like to do the problems if they are set up for me - I don't understand word problems

• I am really struggling with this topic

Round 23.542 to the nearest tenth.

• 23.5

• 23.6

• 23.54

• 23