Multiple choice

Minu is faster than Tinu. Minu and Tinu each walk 240 km. The sum of their speeds is 70 km/hr and the sum of times taken by them is 14 hours. Then, Tinu's speed is equal to?

  1. 20 km/hr

  2. 40 km/hr

  3. 30 km/hr

  4. 35 km/hr
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C Correct answer
Explanation

Let speeds be M and T. M+T=70. Time = 240/M + 240/T = 14 => 240(M+T)/(MT) = 14 => 240(70)/(MT) = 14 => MT = 1200. We have M+T=70 and MT=1200. Quadratic: x^2 - 70x + 1200 = 0 => (x-30)(x-40)=0. Speeds are 30 and 40. Since Minu is faster, M=40, T=30.

AI explanation

Let Tinu's speed be x km/hr and Minu's speed be y km/hr; therefore, x plus y equals 70 and 240 divided by x plus 240 divided by y equals 14. Substituting y as 70 minus x gives 240 divided by x plus 240 divided by (70 minus x) equals 14. Solving this quadratic equation yields the roots 30 and 40, and since Minu is faster, Tinu's slower speed is 30 km/hr.

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