A shop recorded total sales of $2,000 on Monday. On Tuesday, its sales fell by 10%. On Wednesday, sales fell by another 20% compared with Tuesday. From Wednesday to Thursday, sales increased by an amount equal to 25% of Monday’s total sales.

What is the net change, in dollars, in total sales from Monday to Thursday?

Question

A shop recorded total sales of $2,000 on Monday. On Tuesday, its sales fell by 10%. On Wednesday, sales fell by another 20% compared with Tuesday. From Wednesday to Thursday, sales increased by an amount equal to 25% of Monday’s total sales.

What is the net change, in dollars, in total sales from Monday to Thursday?

Mercury · Answer

start with 2,000 for Monday

to represent the Tuesday 10% fall, we let Tuesday = Monday - (0.10*Monday)

on Wednesday, it falls 20% **from the Tuesday price** so you'll take the Tuesday price, and calculate Wednesday = Tuesday - (0.20)*Tuesday

important: *do not use Monday's price in this calculation*

on Thursday, it increased by 25% of Monday's sales. so calculate Monday * 0.25, then add this to the Wednesday price

now, since it's asking for the net change from Monday to Thursday, simply subtract (Thursday - Monday)'s price