A zoo counts its animals - OCR - GCSE Maths - Question 10 - 2023 - Paper 5

Let the number of antelope be denoted as A. From the information given, the number of meerkats (M) is 15 more than the number of antelope: $M = A + 15$

From the ratio of meerkats to zebra, which is 7:3, we can express this as: $\frac{M}{Z} = \frac{7}{3}$ Where Z is the number of zebra.

Substituting the expression for M: $\frac{A + 15}{Z} = \frac{7}{3}$

Cross-multiplying gives: $3(A + 15) = 7Z$

Substituting A from the first part (using the ratio derived previously, where A = 3x and Z = 2x): $3(3x + 15) = 7(2x)$ This simplifies to: $9x + 45 = 14x$ $45 = 14x - 9x$ $x = 9$

Thus, using x = 9 to find the number of zebra, Z = 2x: $Z = 2(9) = 18$

Therefore, the number of zebra in the zoo is 18.