## Estimation in Calculations with Decimal Numbers

Practice Unlimited Questions

#### 1.  Jim spent \$3.85 on pens, \$4.68 on notebooks, \$8.15 on paints and \$2.06 on folders. How much money did he spend altogether? Estimate your answer without using a calculator. Then, use a calculator to find the exact sum of money that Jim spent.

Pens  =  \$3.85
Notebooks  =  \$4.68
Paints  =  \$8.15
Folders  =  \$2.06
Using estimation
Total  =  \$3.85  +  \$4.68  +  \$8.15  +  \$2.06
=  \$4  +  \$5  +  \$8  +  \$2
=  19
So, Jim spent approximately \$19 altogether.
Round off each decimal number to the nearest whole number by studying the digit in the tenths place (first place after the decimal point).
Using calculator
Total  =  \$3.85  +  \$4.68  +  \$8.15  +  \$2.06
=  \$18.74
So, Jim spent exactly \$18.74 altogether.
When we compare the two answers, we see that \$19 (the estimated answer) is close to \$18.74 (the exact answer). So, \$19 is a reasonable estimate.

#### 2. A rectangular plot measures 12.23 m by 9.88 m. Estimate the area of the plot. Then using a calculator find the exact area. Explain the two answers.

Length  =  12.23 m