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

1. Peter and his family used 25 units of electricity in February. How much did they pay for the usage of electricity in February?
2. Shiyun and her family paid $181.20 for the usage of electricity in March. How many units of electricity did they use in March?

(a)
Amount that Peter and his family paid for the usage of electricity
= 25 x 0.89
= $22.25

(b)
Amount that Shiyun and her family paid for first 40 units of electricity
= 40 x 0.89
= $35.60

Amount that Shiyun and her family paid for next 40 units of electricity
= 40 x 1.47
= $58.80

Amount that Shiyun and her family paid for the remaining units of electricity
= 181.20 - 35.60 - 58.80
= $86.80

Remaining units of electricity that Shiyun and her family used
= 86.80 ÷ 2.17
= 40

Total number of units of electricity that Shiyun and her family used
= 40 + 40 + 40
= 120

Answer(s): (a) $22.25; (b) 120