PSLE
A company offered 100 water heaters at 30% discount during a 7-day sale. The line graph shows the number of water heaters left unsold at the end of each day.

1. On which day was the most number of water heaters sold? Give your answer in this format. (Eg Day 1)
2. What percentage of the 100 water heaters were sold in the first four days of the sale?
3. During the sale, the discounted price of the water heaters was $119. After the sale, the remaining water heaters were sold without discount. What was the total amount of money collected from selling all 100 water heaters?

(a)
The steepest line is from Day 2 to Day 3.

On Day 3, the most number of water heaters was sold.

(b)
Number of water heaters that were left at Day 4 = 50

Number of water heaters that were sold for the first four days
= 100 - 50
= 50

Percentage of water heaters that were sold for the first four days
= ⁵⁰₁₀₀ x 100%
= 50%

(c)
Number of water heaters that were left at the end of the sale = 25

Number of water heaters that were sold during the sale
= 100 - 25
= 75

Total amount that collected from the water heaters sold
= 75 x 119
= $8925

Price of each water heater after 30% discount 
= 100% - 30%
= 70%

70% of the price = 119
1% of the price = 119 ÷ 70 = 1.7
100% of the price = 100 x 1.7 = 170

Amount collected from selling the remaining water heaters
= 25 x 170
= $4250

Total amount collected from selling all the 100 water heaters
= 8925 + 4250
= $13175

Answer(s): (a) Day 3; (b) 50%; (c) $13175