Two candidates contested in an election. 80% of the voters cast their votes, out of which 5% of the polled votes were invalid. The winning candidate got 70% of valid votes and won by a majority of 36,480 votes. Find the total number of voters.
- (a)1,18,000
- (b)1,15,000
- (c)1,20,000
- (d)1,25,000
Answer
Why
Correct — C. Let the total number of voters be V and apply the percentages one layer at a time.
Votes polled = 80% of V = 0.80 V
Valid votes = 95% of the polled votes = 0.95 × 0.80 V = 0.76 V
Winner 70%, loser 30%, so the majority is 40% of the valid votes.
Majority = 0.40 × 0.76 V = 0.304 V
0.304 V = 36,480
V = 36,480 ⁄ 0.304 = 1,20,000 → option (c).
Why the others are wrong
- (a)1,18,000 — 1,18,000 voters would produce a majority of 0.304 × 1,18,000 = 35,872 votes, which falls 608 short of the 36,480 the stem states.
- (b)1,15,000 — 1,15,000 yields 0.304 × 1,15,000 = 34,960, a shortfall of 1,520 votes. Nothing in the chain of filters can make up that gap.
- (d)1,25,000 — 1,25,000 yields 0.304 × 1,25,000 = 38,000, overshooting the stated majority by 1,520 votes.
Concept
An election percentage stem is a chain of filters, each applied to whatever survived the previous one.
Total voters → those who polled (80%) → those whose votes were valid (95% of the polled) → the split between the two candidates (70 : 30).
The fact that decides the item is that the majority is the winner's share minus the loser's, that is 70% − 30% = 40% of the valid votes, not 70% of them.
Multiply the three fractions in order — 0.80 × 0.95 × 0.40 = 0.304 — and the whole chain collapses into one number.
There are only two candidates. That is what lets you write the loser's share as 100% − 70%, and it is why the majority is 40% of the valid votes.
Put a third candidate on the ballot and the same arithmetic breaks, because the runner-up's share would no longer be the remainder.
Key facts
- Between two candidates, majority = (winner's % − loser's %) of the valid votes.
- Invalid votes are counted out of the votes polled, not out of the total electorate.
- Here 0.80 × 0.95 × 0.40 = 0.304, so the majority is 30.4% of the total number of voters.
- 36,480 ⁄ 0.304 = 1,20,000 voters.
Study next
Common traps
- Taking the 5% invalid votes out of the total voters instead of out of the votes polled
- Using the winner's 70% as the majority instead of the 40% difference
- Answering with the number of valid votes when the stem asks for the number of voters
SSC stacks two or three filters — turnout, invalid votes, then the winner's share — and asks for whichever quantity is left out.
A heavier version with a 42 : 58 split and a 45,360 majority runs at 23 Sep 2024, 12:30, Quant Q.25. A stripped-down one that states all polled votes are valid is at 18 Sep 2024, 12:30, Quant Q.17.
Related PYQs
No directly related past PYQ was found.