The charge for electricity consumption (E) is partly constant and partly varies as the number of (N) units used. The charge for 163 units is #453.8 while the charge for 42 units is #139.20. Calculate the charge per unit of electricity and obtain a formulae for E in terms of N

Answer 1

E(n) = xN + c
453.8 = 163N + c
139.2 = 42N + c
subtract them:
314.6 = 121N
N = 2.6

sub into 139.2 = 42N + c to find c

rewrite
E(n) = xN + c , replacing N and c with what we found

Answer 2

Finish the solving

Answer 3

Solve and obtain the formula for E in terms of N ( b) calculate the charge per unit of electricity

Answer 4

Finish the solving