Percent Change Day 4:Recovering the original

and new amounts.

By Jim Olsen, W.I.U.#P23

If given the amount of change and percent change:

Use

Then do the algebra steps to find the original amount.

amount of changePercent change

original amount

In percent change situations, there are four numbers to pay attention to:

1. Original amount (the “old”/“starting” amount before the change)

2. New amount (the “ending” amount after the change)3. Amount of change (the difference [subtract] between

original and new)4. Percent change (percent increase or decrease).

Recall from Day 1

Put the known numbers in the chart,then figure out the others.

I consider the case when the amount of change and the percent change are given (and both the original and new amounts are unknown) to be the second of the two harder percent change problem types.

Percent change is used in almost every aspect of life to describe change – and

our world is changing!

Examples:1. Profit for Wilson Manufacturing is up $2,400, which is

a 4% increase, compared to last year. What was the profit last year and the profit this year?

amt. of changeUse Percent change =

original amt.

2400 .04

Do the algebra: .04x = 2400

2400

.04Original amount $60,000 (last year)

This yea

x

x

x

r's profit = 60,000+2400 = $62,400

Examples:2. The average number of turnovers during the second half

of the season was down 4.2 turnovers, which is a 35% decrease. Find the turnover average in the first half of the season and in the second half of the season?

amt. of changeUse Percent change =

original amt.

4.2 .35

Do the algebra: .35x = 4.2

4.2

.35Original amount 12 turnovers (1st half)

2nd

x

x

x

half: 12 - 4.2 7.8 turnovers

Closing Notes Remember

#P23

If given the amount of change and percent change:

Use

Then do the algebra steps to find the original amount.

amount of changePercent change

original amount

Stay tuned…

This is Day 4 of 4.

Learnist board: http://bit.ly/13AGhZq