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Mental Math
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100

Simone saved $15.45 from her allowance, had $7.37 in her piggy bank, and had $22.55 left from her birthday. How much money does Simone have?

Which mental math strategies will help her find the total? Select all that apply.

Responses

  • Add $0.45 and $0.55 to make a dollar. Then, $7 + $22 + $1 = $30. Next, $30 + $15 = $45. Finally, add $0.37 to get $45.37.

  • Drop all of the cents for each dollar amount. Then, $15 + $7 + $22 = $44.

  • Round each dollar amount to the nearest dollar. Then, $7 + $23 = $30. Finally, $30 + $15 = $45.

  • Add $0.05 to $15.45 to make $15.50. Subtract $0.05 from $22.55 to make $22.50. Then, $15.50 + $22.50 = $38. Finally, $38 + $7.37 = $45.37.

1 and 4 

100

Which explains how to find the sum of the decimals?

  • Count 40 shaded squares, or 0.40, on the first grid and 80 shaded squares, or 0.80, on the second grid. Then add them together to get 1.20.

  • Count 44 shaded squares, or 0.44, on the first grid and 87 shaded squares, or 0.87, on the second grid. Then add them together to get 1.31.

  • Count 56 shaded squares, or 0.56, on the first grid and 13 shaded squares, or 0.13, on the second grid. Then add them together to get 0.69.

  • Count a total of 100 squares, or 1.00, on the left grid and 100 squares, or 1.00, on the right grid. Then add them together to get 2.00.

2

100


Miles bought three books that cost $13.89, $6.70, and $3.05. What is the total amount Miles spent on the books?

1.) $22.54

2.) $22.64

3.) $23.54

4.) $23.64

4

100

Brady drew a rectangle with an area of 35.52 square centimeters. Staci drew a rectangle with an area of 61.44 square centimeters. How many more square centimeters is Staci's rectangle than Brady's? 

  • 25.08 square centimeters

  • 25.92 square centimeters

  • 26.08 square centimeters

  • 26.82 square centimeters

2

100

Sage and Claire found the difference of 2.3 and 1.04. Sage gave the answer of 1.26. Claire gave the answer of 1.34. Complete the statement below to show which student is correct.

_________ found the correct difference of 2.3 and 1.04. 

Sage

200

1.) 227.4+213.5          Choices: 440, 460, 410, 430

2.) 513.9−46.1

3.) 348.2+62.8

4.) 637.9−206.3


1 - 440, 2 - 460, 3 - 410, 4 - 430 

200

Carter bought a fishing pole for $34.80 and a tackle box for $17.49.

What is the total amount Carter spent on both items?


$52.29