PSLE
A company offered $(dn0) lamps at 20% discount during a 7-day sale. The line graph shows the number of lamps left unsold at the end of each day.

1. On which day was the most number of lamps sold? Give your answer in this format. (Eg Day 1)
2. What percentage of the 200 lamps were sold in the first six days of the sale?
3. During the sale, the discounted price of the lamps was $48. After the sale, the remaining lamps were sold without discount. What was the total amount of money collected from selling all 200 lamps?

(a)
Steepest line is from Day 3 to Day 4.

On Day 4, the most number of lamps was sold.

(b)
Number of lamps that were left at Day 6 = 60

Number of lamps that were sold for the first six days
= 200 - 60
= 140

Percentage of lamps that were sold for the first six days
= ¹⁴⁰₂₀₀ x 100%
= 70%

(c)
Number of lamps that were left at the end of the sale = 40

Number of lamps that were sold during the sale
= 200 - 40
= 160

Total amount that collected from the lamps sold
= 160 x 48
= $7680

Price of each lamp after 20% discount 
= 100% - 20%
= 80%

80% of the price = 48
1% of the price = 48 ÷ 80 = 0.6
100% of the price = 100 x 0.6 = 60

Amount collected from selling the remaining lamps
= 40 x 60
= $2400

Total amount collected from selling all the 200 lamps
= 7680 + 2400
= $10080

Answer(s): (a) Day 4; (b) 70%; (c) $10080