Answer: B Let the original speed be S and time be T If new speed = S*3/4, then new time would be T*4/3. (D = ST = Constant). Given, 3T/4 - T = 20T/3 => T= 60 minutes = 1 hour
Q. No. 2:
A motorboat whose speed is 15 km/hr in still water goes 30km downstream and comes back in four and a half hours. The speed of the stream is
Answer: D Let the speed of the stream be 's' km/hr. Then, upward speed = (15-s) km/hr and downward speed = (15+s) km/hr Therefore, 30/(15+s) + 30/(15-s) = -4.5 On solving this equation we get, s= 5km/hr.
Q. No. 3:
A passenger train takes two hours less for a journey of 300km if its speed is increased by 5km/hr from its normal speed. The normal speed is
Answer: C Let the normal speed be 's' km/hr Then new speed = (s+5) km/hr 300/s - 2 = 300/(s+5) On solving this equation we get s = 25km/hr
Q. No. 4:
A race course is 400 m long. A and B run a race and A wins by 5m. B and C run over the same course and B win by 4m. C and D run over it and D wins by 16m. If A and D run over it, then who would win and by how much?
Answer: A If A covers 400m, B covers 395 m If B covers 400m, C covers 396 m If D covers 400m, C covers 384 m Now if B covers 395 m, then C will cover 396/400 * 395 = 391.05m If C covers 391.05 m, then D will cover 400/384 * 391.05 = 407.24 If A and D run over 400 m, then D win by 7.2 m(approx).
Q. No. 5:
Wheel of diameter 7cm and 14 cm start rolling simultaneously from X and Y which are 1980cm apart towards each other in opposite directions. Both of them make same number of revolutions per second. If both of them meet after 10s, the speed of the smaller wheel is
Answer: C Circumference of the smaller wheel (X) = 2*pie * 3.5 = 22m Circumference of the bigger wheel (Y) = 2*pie*7 = 44 m Let both the wheels make x revolutions in one second Distance covered by both the wheel in 1 second = 22x+44x= 66x Distance covered by both wheels in 10 second = 660x. Given, 660x = 1980 =>x= 3 Speed of smaller wheel = 22x = 22*3 = 66 cm/s
Q. No. 6:
The jogging track in a sports complex is 726 m in circumference. Suresh and his wife start from the same point and walk in opposite direction at 4.5 km/hr and 3.75 km/hr respectively. They will meet for the first time in
Answer: D Let both of them meet after T min 4500 m are covered by Suresh in 60 m. In T min he will cover 4500T/60 Likewise, In T min Suresh's wife will cover 3750T/60 Given, 4500T/60 + 3750T/60 = 726 T = 5.28 minutes.