A household's electricity bill is a fixed line rent plus a charge for every unit consumed. In one month 180 units were used and the bill was Rs 960; the next month 300 units were used and the bill was Rs 1440. Find the fixed line rent (in Rs).

Question

Accepted Answer

240. Let the line rent be Rs x and the rate Rs y per unit. x + 180y = 960 and x + 300y = 1440. Subtracting: 120y = 480, so y = 4 and x = 960 - 720 = 240. Check: 240 + 300 x 4 = 1440. 4 is the per-unit rate, the other unknown; 480 is the difference between the two bills, not the rent; 720 is the usage part of the first month's bill.

A household's electricity bill is a fixed line rent plus a charge for every unit consumed. In one month 180 units were used and the bill was Rs 960; the next month 300 units were used and the bill was Rs 1440. Find the fixed line rent (in Rs).

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