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4.Average
hard
An aeroplane travels $2500 \,km , 1200 \,km$ and $500\,km$ at $500\, km / h \,, 400 \,km $ and $250\,km / h $ respectively. The average speed is:(in $km/h$)
A
$420$
B
$410$
C
$405$
D
$575$
Solution
The total time taken can be calculated as shown below:
| Distance | Speed | Time |
| $2500 \,km$ | $500 \,km/h$ | $5\, hrs$ |
| $1200 \,km$ | $400 \,km/h$ | $3\, hrs$ |
| $500 \,km$ | $250 \,km/h$ | $2\, hrs$ |
|
Total $4200\,km$ |
$10\,hrs$ |
Average speed $=\frac{4200}{10}=420 Km / h$
Standard 13
Quantitative Aptitude
