Mohan covers a distance of 187 km at the speed of S km/hr. If Mohan increases his speed by 6 km/hr, then he takes 6 hours less. What is the value of S?
Show answer & explanation
Correct answer: C
Explanation
The correct answer is option 3 i.e. 11 km/hr.
| Understanding/Application |
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Distance = 187 km Initial Speed = S km/hr Let Initial time = T hours Speed(Time) = Distance ST = 187 km New speed = (S + 6) km/hr New Time = (T - 6) km/hr Then, (S + 6)(T - 6) = 187 ST - 6S + 6T - 36 = 187 Substituting ST = 187, 187 - 6S + 6T - 36 = 187 6T - 6S = 36 T - S = 6 Substituting T = 187/S (187/S) - S = 6 187 - S2 -6S = 0 S2 + 6S - 187 = 0 S2 - 11S + 17S - 187 = 0 S(S - 11) + 17(S - 11) = 0 (S - 11) (S + 17) = 0 S = 11 or -17 |
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Speed can never be negative. Speed of Mohan = 11 km/hr |