Estimating a Decimal Sum or Difference

Problem 1

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

Problem 2

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