Estimating a Decimal Sum or Difference



Estimate the sum after rounding each number to the nearest tenth

98.09 + 23.41 − 11.30 – 27.85

Solution

Step 1

Rounding each term to nearest tenth, the expression becomes

= 98.09 + 23.41 − 11.30 – 27.85

= 98.1 +23.4 – 11.3 – 27.9

= 121.5 −39.2 = 82.3

Step 2

So the estimated sum after rounding each number to the nearest tenth

= 98.09 + 23.41 − 11.30 – 27.85 = 82.3

Estimate the difference after rounding each number to the nearest tenth/hundredth 69.07 + 15.41 − 8.30 – 7.85

Solution

Step 1

Rounding each term to nearest tenth, the expression becomes

= 69.07 + 15.41 − 8.30 – 7.85

= 69.1 +15.4 – 8.3 – 7.9

= 84.5 −16.2 = 68.3

Step 2

So the estimated sum after rounding each number to the nearest tenth

= 69.07 + 15.41 − 8.30 – 7.85 = 68.3



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