Question

A box containing blue and white balls has 29 balls, in total. If the number of white balls is 21, find the number of blue balls.

• A. 8
• B. 9
• C. 11
• D. 7

Answer 1

The correct option is A 8

Let the number of blue balls in the box be 'x'.

Given :
Number of white balls = 21.
Total number of balls in the box = 29

We know,
$\text{Number of Blue balls + Number of White balls =}$
$\text{Total number of balls in the box}$

By putting the values, we can write:

$\text{Blue balls}+\text{White balls}=\text{Total balls}$

$x+21=29$
$-21=-21$
$-------------$
$x=8$

∴ The number of blue balls in the box will be (x) = 8.