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SSC CHSL 2023 PYQ — Question 63

SSC CHSL - 09 March 2023 - Shift 3 • Quantitative Aptitude • Q63

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A car left 60 minutes early than the scheduled time but in order to reach its destination 280 km away in time, it has to slow its usual speed by 14 km/hr. What is the usual speed of the car?

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Correct answer: B

Explanation

The correct answer is Option 2 i.e. 70 km/hr.

Let the usual speed of the car be S km/hr.

So, 280/(S - 14) = 280/S - 1

⇒ [280S - 280(S - 14)]/[S(S - 14)] = -1

⇒ (280S - 280S + 3920)/(S2 - 14S) = -1

⇒ S2 - 14S - 3920 = 0

⇒ S=−(−14)±(−14)2−(4×1×−3920)2×1=14±196+156802S=\frac{-(-14)\pm \sqrt{(-14)^2-(4\times 1\times -3920)}}{2\times 1}=\frac{14\pm \sqrt{196+15680}}{2}

=14±158762=\frac{14\pm \sqrt{15876}}{2}

= (14 + 126)/2 or (14 - 126)/2

= 70 or - 56 [Not possible]

Hence, the usual speed of the car is 70 km/hr.