Question

A mobile company offers two plans. The plan A costs Rs.300 and offers 1100 free minutes per month with a charge of 15 paise per minute for every additional minute. Plan B costs Rs. 400 and offers 1300 free minutes per month with a charge of 10 paise per minute for every additional minute. Let x and y represent the total cost per month for the plan A and the plan B respectively, where t represents the number of minutes used. If Sneha uses 2500 minutes per month, then what will be the value of x-y?

Answer 1

The costs are (assuming 1 Rs) = 100 paise)
A: 300+0.15(t-1100)
B: 400+0.10(t-1300)
So now plug in t=2500 and calculate x-y

Answer 2

x = 300 + 0.15 (2500 - 1100)
= 300 + 0.15 x 1400
= 300 + 210
= 510

y = 400+ 0.10 (2500 - 1300)
= 400 + 0.10 x 1200
= 400 + 120
= 520
∴ x - y = 510 - 520 = -10