Question

$\text{Total time taken to repair three cars is}4\frac{8}{10}\text{hours. If the time taken for the first two cars}\text{is}1\frac{1}{10}\text{and}2\frac{1}{10}\text{hours respectively, then how}\text{long does it take to repair the third car?}$

• A. $1\frac{1}{10}\text{hours}$
• B. $1\frac{2}{5}\text{hours}$
• C. $1\frac{3}{5}\text{hours}$
• D. $1\frac{3}{10}\text{hours}$

Answer 1

The correct option is C $1\frac{3}{5}\text{hours}$

$\text{Total time taken to repair all three cars}=4\frac{8}{10}\text{hours}$

$\text{Time taken to repair car 1}=1\frac{1}{10}\text{hours}$

$\text{Time taken to repair car 2}=2\frac{1}{10}\text{hours}$

$\therefore \text{Total time taken to repair cars 1 and 2}=(1\frac{1}{10}+2\frac{1}{10})\text{hours}$

$=\left[\right(1+2)+(\frac{1}{10}+\frac{1}{10}\left)\right]\text{hours}$

$=[3+\frac{(1+1)}{10}]\text{hours}$

$=[3+\frac{2}{10}]\text{hours}$

$=3\frac{2}{10}\text{hours}$

$\text{Now,}$


$⟹\text{Time taken for the 3rd car's repair}$

$=4\frac{8}{10}-3\frac{2}{10}$

$=(4-3)+(\frac{8}{10}-\frac{2}{10})$

$=1+\frac{(8-2)}{10}$

$=1+\frac{6}{10}$

$=1+\frac{6÷2}{10÷2}$

$=1+\frac{3}{5}$

$=1\frac{3}{5}$

$\therefore \text{The time taken to repair the third car}\text{is}1\frac{3}{5}\text{hours.}$