Given: Three-tenth of total voters promised to vote for A and the rest promised to vote for B. On the last day of the election, 20% of voters went back of their promise to vote for A and 25% of voters went back of their promise to vote for B. A lost the election by 850 votes. Calculation: Let the total number of voters be x. Three-tenth of total voters promised to vote for A and the rest promised to vote for B. Voters who promised to vote for A = 3x/10 Total voters = Voters who promised to vote for A + Voters who promised to vote for B ⇒ x = 3x/10 + Voters who promised to vote for B ⇒ Voters who promised to vote for B = x – 3x/10 = 7x/10 On the last day of the election, 20% of voters went back of their promise to vote for A and 25% of voters went back of their promise to vote for B. Number of voters who backed out for A = 20% of 3x/10 = 3x/50 Number of voters who backed out for B = 25% of 7x/10 = 7x/40 Number of votes obtained by A = Voters who promised to vote for A + Number of voters who backed out for B - Number of voters who backed out for A ⇒ 3x/10 + 7x/40 – 3x/50 = 83x/200 Number of votes obtained by B = Voters who promised to vote for B + Number of voters who backed out for A - Number of voters who backed out for B ⇒ 7x/10 + 3x/50 – 7x/40 = 117x/200 A lost the election by 850 votes. ⇒ (117x/200) – (83x/200) = 850 ⇒ 34x/200 = 850 ⇒ x = 850 × 200/34 ⇒ x = 5,000 ∴ Total number of voters were equal to 5,000.