PSLE
A company offered 72 speakers at 10% discount during a 7-day sale. The line graph shows the number of speakers left unsold at the end of each day.

1. On which day was the most number of speakers sold? Give your answer in this format. (Eg Day 1)
2. What percentage of the 72 speakers were sold in the first four days of the sale?
3. During the sale, the discounted price of the speakers was $45. After the sale, the remaining speakers were sold without discount. What was the total amount of money collected from selling all 72 speakers?

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

On Day 3, the most number of speakers was sold.

(b)
Number of speakers that were left at Day 4 = 36

Number of speakers that were sold for the first four days
= 72 - 36
= 36

Percentage of speakers that were sold for the first four days
= ³⁶₇₂ x 100%
= 50%

(c)
Number of speakers that were left at the end of the sale = 16

Number of speakers that were sold during the sale
= 72 - 16
= 56

Total amount that collected from the speakers sold
= 56 x 45
= $2520

Price of each speaker after 10% discount 
= 100% - 10%
= 90%

90% of the price = 45
1% of the price = 45 ÷ 90 = 0.5
100% of the price = 100 x 0.5 = 50

Amount collected from selling the remaining speakers
= 16 x 50
= $800

Total amount collected from selling all the 72 speakers
= 2520 + 800
= $3320

Answer(s): (a) Day 3; (b) 50%; (c) $3320