## Solution
Speed downstream = d/t = 75/(2 1/2) = 30 kmph
Speed upstream = d/t = 45/(2 1/2) = 18 kmph
The speed of the stream = (30 - 18)/2 = 6 kmph
## What the question and answer could be
A man rows his boat 75 km downstream and 45 km upstream, taking 2 1/2 hours each time. Find the speed of the stream?
Options:
(A) 1 kmph
(B) 6 kmph
(C) 5 kmph
(D) 8 kmph
(E) 7 kmph
(B)

## Solution
I think answer on this one should be B too. Since we know that 14^7>15^4, as Will said one should always check if the number is positive.
## What the question and answer could be
What is the units digit of the expression 14^715^4?
Options:
(A) 0
(B) 8
(C) 4
(D) 6
(E) 3
(B)

## Solution
Increase = (60/60)*100 = (6/6)*100 = 100%.
## What the question and answer could be
John makes $60 a week from his job. He earns a raise and now makes $120 a week. What is the % increase?
Options:
(A) 16%
(B) 100%
(C) 17%
(D) 17.61%
(E) 17.56%
(B)

## Solution
Number of ways of choosing 4 stocks = 8C4
Number of ways of ranking the chosen stocks = 4!
Hence total ways of chosing and ranking = 8C4 * 4! = 1680
## What the question and answer could be
An equity analyst needs to select 4 stocks for the upcoming year and rank these securities in terms of their investment potential. If the analyst has narrowed down the list of potential stocks to 8, in how many ways can she choose and rank her top 4 picks?
Options:
(A) 1200
(B) 1680
(C) 2102
(D) 4020
(E) 1840
(B)