The monthly telephone bill has a fixed tariff for upto 100 outgoing calls. Outgoing call in excess of 100 are charged at a certain fixed rate per call. The monthly bills of Rajesh and Suraj who made 196 outgoing calls and 436 outgoing calls respectively were Rs. 600 and Rs. 900 respectively. Find the monthly bill for a person who has made 320 outgoing calls (in Rs. )
Explanation:
Let the fixed tariff be F and the number of outgoing calls be C.
Let the charge per call for calls in excess of 100 be k.
If C > 100, the call charge is in the form k(C - 100).
600 = F + k(96) → (1)
900 = F + k(336) → (2)
Subtracting (1) from (2), 300 = 240k
k = 5/4 & F = 480
Required monthly bill = F + k(220) = 480 + (5/4) × 220 = Rs. 755
Hence, 755.
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