1. A boat can travel with a speed of 13 km/hr in still water. If the speed of the stream is 4 km/hr, find the time taken by the boat to go 68 km downstream.
A. 2 hours
B. 3 hours
C. 4 hours
D. 5 hours
Answer: Option C
Explanation:
Speed downstream = (13 + 4) km/hr = 17 km/hr.
Time taken to travel 68 km downstream = [latex]\frac {68}{17}[/latex]hrs = 4 hrs
2. A man's speed with the current is 15 km/hr and the speed of the current is 2.5 km/hr. The man's speed against the current is:
A. 8.5 km/hr
B. 9 km/hr
C. 10 km/hr
D. 12.5 km/hr
Answer: Option C
Explanation:
Man's rate in still water = (15 - 2.5) km/hr = 12.5 km/hr.
Man's rate against the current = (12.5 - 2.5) km/hr = 10 km/hr.
3. What least number must be added to 1056, so that the sum is completely divisible by 23 ?
Answer: Option A
Explanation:
23) 1056 (45
92
---
136
115
---
21
---
Required number = (23 - 21)
= 2.
4. How many of the following numbers are divisible by 132 ?
264, 396, 462, 792, 968, 2178, 5184, 6336
Answer: Option A
Explanation:
132 = 4 x 3 x 11
So, if the number divisible by all the three numbers 4, 3 and 11, then the number is divisible by 132 also.
264 11,3,4 (/)
396 11,3,4 (/)
462 11,3 (X)
792 11,3,4 (/)
968 11,4 (X)
2178 11,3 (X)
5184 3,4 (X)
6336 11,3,4 (/)
Therefore the following numbers are divisible by 132: 264, 396, 792 and 6336.
Required number of number = 4.
5. 331, 482, 551, 263, 383, 362, 284
A. 263
B. 383
C. 331
D. 551
Answer: Option B
Explanation:
In each number except 383, the product of first and third digits is the middle one.