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JAMB Mathematics 2021 Paper

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Question : 28

Total: 40

A car travels from calabar to Enugu, a distance of P km with an average speed of U km per hour and continues to benin, a distance of Q km, with an average speed of Wkm per hour. Find its average speed from Calabar to Benin

$\frac{p + q}{pw + qu}$
$\frac{uw(p + q)}{pw + qu}$
$\frac{uw(p + q)}{pw}$
$\frac{uw}{pw + qu}$

Solution:

Average speed = $\frac{\text{total Distance}}{\text{Total Time}}$

from Calabar to Enugu in time t1, hence

t1 =

\frac{P}{U}

Also from Enugu to Benin

t2

\frac{q}{w}

Av. speed =

\frac{p + q}{t_1 + t_2}

=

\frac{p + q}{\frac{p}{u} + \frac{q}{w}}

= p + q x

\frac{uw}{pw + qu}

=

\frac{uw(p + q)}{pw + qu}

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