Question

(7.) A car goes from A to B in 3 hours. If its average speed had been 9 km/h an hour slower, it would have taken
4 hours. Find the distance of B from A.
​

Answer 1

Answer:

$\red { The \: distance \: of \: B \:from \: A }$

$\green { = 108 \:km}$

Step-by-step explanation:

$Let \: the \: speed \: of \: car = s \: km/h$

$\underline { If \: the \: car \: goes \: from \: A \:to \: B }$

$Time = 3 \: hours$

$Distance = d \: km$

$\implies s = \frac{d}{3} \: ---(1)$

$\underline { If \: average \: speed \: had \: slower }$

$New \: speed = (s-9) \: km/h$

$Time = 4 \: hours$

$\implies s-9 = \frac{d}{4}$

$\implies s = \frac{d}{4} + 9 \: ---(2)$

/* From (1) and (2)

$\implies \frac{d}{3} = \frac{d}{4} + 9$

$\implies \frac{d}{3} - \frac{d}{4} = 9$

$\implies \frac{4d-3d}{12} = 9$

$\implies \frac{d}{12} = 9$

$\implies d = 9 \times 12 = 108 \:km$

Therefore.,

$\red { The \: distance \: of \: B \:from \: A }$

$\green { = 108 \:km}$

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