In a box of marbles, there are three less white marbles than the red ones and five more white marbles than the green ones. If there are a total of 10 white marbles, how many marbles are there in the box ?
- (a) 26
- (b) 28 ✓ UPSC's answer
- (c) 32
- (d) 36
Why the answer is (b)
• Let the number of white marbles be W, red marbles be R, and green marbles be G.
• The problem states there are 10 white marbles, so W = 10.
• There are three less white marbles than red ones, meaning W = R - 3, so R = W + 3 = 10 + 3 = 13.
• There are five more white marbles than green ones, meaning W = G + 5, so G = W - 5 = 10 - 5 = 5.
• The total number of marbles is the sum of white, red, and green marbles: 10 + 13 + 5 = 28.
• Therefore, the correct option is (b).
Why the other options are wrong
- (a) 26
- Option (a) is incorrect because the total sum of 26 does not match the calculated total of 28.
- (c) 32
- Option (c) is incorrect because the total sum of 32 does not match the calculated total of 28.
- (d) 36
- Option (d) is incorrect because the total sum of 36 does not match the calculated total of 28.
Asked in the CSAT Paper II of the UPSC Civil Services Preliminary Examination 2015, held on 23 August 2015. Question and answer key: Union Public Service Commission. Explanation: UPSC Answer Check.