Question

10(a). The cost C of feeding some students in a class is partly constant and partly varies as the number of students n. For 8 students the cost is $70.00 and for 10 students the cost is $90.00. Find:
(i) An expression for C in terms of n.
(ii) The cost of feeding 12 students.

Accepted Answer

(i) C = K₁ + K₂n
   K₁ + 8K₂ = 70 ...(1)
   K₁ + 10K₂ = 90 ...(2)
   2K₂ = 20 → K₂ = 10; K₁ = −10
   ∴ C = −10 + 10n

(ii) When n = 12:
   C = −10 + 10(12) = $110.00

WAEC Mathematics 2025 Theory — Question 11

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