A, B and C are three parties which contests in local election (people vote for one of the three parties alone). A and B forms an alliance thinking that they will get 50% more votes than C due to which 20% of voters from party A vote for party C and 15000 votes from party B vote for party C. Now C gets 56 2/3% of the total vote casted whereas only 16 2/3% of the voters only voted for party B? What is the initial amount of vote bank that party A had before alliance?
A, B and C are three parties which contests in local election (people vote for one of the three parties alone). A and B forms an alliance thinking that they will get 50% more votes than C due to which 20% of voters from party A vote for party C and 15000 votes from party B vote for party C. Now C gets 56 2/3% of the total vote casted whereas only 16 2/3% of the voters only voted for party B? What is the initial amount of vote bank that party A had before alliance? Correct Answer 50000
Let the amount of original vote bank for party A, B and C be a, b and c respectively.
Due to alliance 20% of voters from A votes to party C and 15000 from party B to party C
So, Remaining vote for A = 80% of a = 0.8a
Remaining vote for B = b – 15000
Vote for C = c + 0.2a + 15000
% of vote of party C = ((c + 0.2a + 15000) / (a + b + c)) × 100
⇒ (170/3) = ((c + 0.2a + 15000) / (a + b + c)) × 100
⇒ 17/3 = ((c + 0.2a + 15000) / (a + b + c)) × 10
⇒ 17a + 17b + 17c = 30c + 6a + 450000
⇒ 11a + 17b = 13c + 450000 ---- 1
% vote by party B = ((b – 15000) / (a + b + c)) × 100
⇒ 16 2/3 = ((b – 15000) / (a + b + c)) × 100
⇒ 50/3 = ((b – 15000) / (a + b + c)) × 100
⇒ a + b + c = 6b – 90000
⇒ a + c = 5b – 90000 ---- 2
Given that (a + c) = 50% more than B
a + b = 1.5c
⇒ a = 1.5c – b
Substituting in equation 1 and 2,
16.5c – 11b + 17b = 13c + 450000
⇒ 3.5c + 6b = 450000 ---- 3
⇒ 1.5c – b + c = 5b – 90000
⇒ 6b – 2.5c = 90000 ---- 4
Subtracting the equations
6c = 360000
⇒ c = 60000
Substituting in equation 3
210000 + 6b = 450000
⇒ b = 40000
∴ a = 1.5c – b = 50000