Chapter 2.3, Problem 40PP

(a)

Interpretation Introduction

Interpretation:

The answer of given addition problem needs to be rounded off if necessary. $43.2\text{cm}+51.0\text{cm}+48.7\text{cm}$

Concept introduction:

To round off a number, look at the digit up to which number needs to be rounded off. If the digit right to it is less than 5 simply add 1 to the previous digit and remove all the digits after it from the number. If the digit right to the digit up to which rounding needs to be done is less than 5, just remove all the digits after it from the number.

Now, if the digit is equal to 5 then 1 is added to the previous digit if it is an odd number. If the previous digit is an even number, simply remove all the digits after it from the number.

Answer to Problem 40PP

The final answer of the given problem is correct to $143\text{cm}$.

Explanation of Solution

When adding the numbers in units should be same for the measurements.

$\begin{array}{c}43.2\text{cm}+51.0\text{cm}+48.7\text{cm}\text{=}142.9\text{cm}\\ \text{=}143\text{cm}\end{array}$

Here the fourth digit is greater than five then add 1 to the digit in the previous place and then remove all the digits to the right.

(b)

Interpretation Introduction

Interpretation:

The answer of given addition problem needs to be rounded off if necessary. $258.3\text{kg}+257.11\text{kg}+253\text{kg}$

Concept introduction:

To round off a number, look at the digit up to which number needs to be rounded off. If the digit right to it is less than 5 simply add 1 to the previous digit and remove all the digits after it from the number. If the digit right to the digit up to which rounding needs to be done is less than 5, just remove all the digits after it from the number.

Now, if the digit is equal to 5 then 1 is added to the previous digit if it is an odd number. If the previous digit is an even number, simply remove all the digits after it from the number.

Answer to Problem 40PP

The final answer of the given problem is correct to $768.41\text{kg}$.

Explanation of Solution

When adding the numbers the digits after decimal should be same. Then the given problem can also be written as:

$258.3\text{kg}+257.11\text{kg}+253\text{kg}=258.30\text{kg}+257.11\text{kg}+253.00\text{kg}$

$258.30\text{kg}+257.11\text{kg}+253.00\text{kg}\text{=}768.41\text{kg}$

Here, the digits after decimal are less than five then there will be rounding off.