# A family in Singapore part 9 (Math Question)

Standard

You should read the posting on understand the concept of Percentage.

Upper primary school mathematics question UPQ148

Sarin’s mother is keeping track of the household expenses. She need to make sure the family’s expenditure is within their means. The line chart below shows their family’s expenditure over five weeks. When was there a 20% decrease in their family’s expenditure?

Solution:

The percentage of decrease is the percentage of decrease in expenditures of two consecutive weeks to the expenditure of the first week of the two weeks.

Base on the line-chart, we can tabulate a table with the weekly decreases and compute the percentage of decreases.

Example:

The different in expenditure from 1st week to 2nd week = 90 – 80 = \$10

The percentage decrease = 10 ÷ 90 × 100% = 11.1%

 Expenditure (\$) Decrease (\$) Decrease (%) 1st week 90 2nd week 80 10 11.1 3rd week 50 30 37.5 4th week 40 10 20.0 5th week 20 20 50.0

From the table, the family expenditure decrease by 20%  from 3rd week to 4th week.