Question

8 Black pencils cost 15e cach and coloured

pencils cost 2lc cach. Ir 24 pencils cost
$4,02, how many of them were black (Hint
let there be + black pencils. Thus there are
24 – x coloured pencils. Work in cents.)
of

Answer 1

17 black pencils

Explanation:

Cost of black pencils; 15 cents each

Cost of colored pencils; 21 cents each

We are told that 24 pencils cost $4.02 = 402 cents

Let black pencils be x and let colored pencils be y.

Thus;

x + y = 24 - - - (eq 1)

Also,

15x + 21y = 402 - - - (eq 2)

From eq 1, y = 24 - x

Thus putting it in eq 2 gives;

15x + 21(24 - x) = 402

15x + 504 - 21x = 402

504 - 402 = 6x

x = 102/6

x = 17