A learning platform charges a fixed monthly fee and an additional cost per digital learning module accessed. A student observes that when she accessed 10 modules, her bill was ₹ 400. When she accessed 14 modules, her bill was ₹ 500. If the monthly bill depends on the number of modules accessed, , according to the relation , find the values of and . [Page No. 27]
Given expression is y = ax + b
When x = 10, y becomes 400 then expression is given by
400 = 10a + b ...(i)
When x = 14, y becomes 500 then expression is given by
500 = 14a + b ...(ii)
Subtract eq. (i) from eq. (ii), we have
500 - 400 = 14a + b - 10a - b
⇒ 100 = 4a
⇒ a = 25
Substitute in eq. (i), we have
b = 400 - 10(25) = 400 - 250 = 150
Hence, the values of a and b are 25 and 150 respectively.
