The table shows the rates charged for the use of electricity in a country.

1. Howard and his family used 35 units of electricity in February. How much did they pay for the usage of electricity in February?
2. Cathy and her family paid $197.80 for the usage of electricity in March. How many units of electricity did they use in March?

(a)
Amount that Howard and his family paid for the usage of electricity
= 35 x 0.84
= $29.40

(b)
Amount that Cathy and her family paid for first 40 units of electricity
= 40 x 0.84
= $33.60

Amount that Cathy and her family paid for next 40 units of electricity
= 40 x 1.18
= $47.20

Amount that Cathy and her family paid for the remaining units of electricity
= 197.80 - 33.60 - 47.20
= $117.00

Remaining units of electricity that Cathy and her family used
= 117.00 ÷ 2.34
= 50

Total number of units of electricity that Cathy and her family used
= 40 + 40 + 50
= 130

Answer(s): (a) $29.40; (b) 130