The cost of dinner for a group of students is partly constant and partly varies directly as the number of students. If the cost is N74.00 when the number of is 20 and N96.00 when the number is 30, find the cost when there are 15 students

  • A N68.50
  • B N63.00
  • C N60.00
  • D N52.00
jamb 1989mathematics

The correct answer is B. N63.00

Let the constant part of the cost be c and the variable part be k. Then, we can write two equations based on the information given:

20k + c = 74 30k + c = 96

Subtracting the first equation from the second, we get:

10k = 22 k = 2.2

Substituting this value of k into the first equation, we get:

20 * 2.2 + c = 74 c = 74 - 44 = 30

So, the cost function is C(n) = 2.2n + 30, where n is the number of students. When there are 15 students, the cost is:

C(15) = 2.2 * 15 + 30 = N63.00

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