Rationale: Speed downstream = d/t = 85/(2 1/2) = 34 kmph
Speed upstream = d/t = 45/(2 1/2) = 18 kmph
The speed of the stream = (34 - 18)/2 = 8 kmph
The answer: (D)
Question: A man rows his boat 85 km downstream and 45 km upstream, taking 2 1/2 hours each time. Find the speed of the stream?
Options:
(A) 2 kmph.
(B) 4 kmph.
(C) 5 kmph.
(D) 8 kmph.
(E) 7 kmph.
Reasoning: 5 choices for each of the 4 questions, thus total of 5*5*5*5 = 5^4 = 625 ways.
Ans: (C)
Question: A multiple choice test consists of 4 questions, and each question has 5 answer choices. In how many ways can the test be completed if every question is unanswered?
Options:
(A) 24
(B) 120
(C) 625
(D) 720
(E) 1024
Rationale: Final number = Initial number + 25%(original number) = 80 + 25%(80) = 80 + 20 = 100.
The answer: (E)
Question: A light has a rating of 80 watts, it is replaced with a new light that has 25% higher wattage. How many watts does the new light have?
Options:
(A) 105
(B) 95
(C) 80
(D) 60
(E) 100
Reasoning: 7g/30 tells us that g is a factor of 30, which has 2, 3, and 5 as its prime factors. Each of them is distinct. Moreover, all multiples of 30 less than 200 can be derived by multiplying these prime factors alone. Thus, number of different prime factors is 3.
Ans: (B)
Question: In g is a positive integer smaller than 200 and (14g)/60 is an integer, then g has how many different positive prime factors?
Options:
(A) 2
(B) 3
(C) 5
(D) 6
(E) 8
Rationale: Part filled by (A + B + C) in 3 minutes = 3(1/30 + 1/20 + 1/10) = 11/20
Part filled by C in 3 minutes = 3/10
Required ratio = 3/10 * 20/11 = 6/11
The answer: (B)
Question: Three pipes A, B and C can fill a tank from empty to full in 30 minutes, 20 minutes and 10 minutes respectively. When the tank is empty, all the three pipes are opened. A, B and C discharge chemical solutions P, Q and R respectively. What is the proportion of solution R in the liquid in the tank after 3 minutes?
Options:
(A) 6/19
(B) 6/11
(C) 6/12
(D) 6/10
(E) 6/38
Rationale: 10 men + 15 women in 1 day do 115 + 112 = 960 work
\ Time taken = 609 days = 623 days
The answer: (C)
Question: 10 men can complete a piece of work in 15 days and 15 women can complete the same work in 12 days. If all the 10 men and 15 women work together, in how many days will the work get completed?
Options:
(A) 6
(B) 7 23
(C) 6 23
(D) 6 13
(E) None of these