Percentage: reverse percent and simple interest

Practice 5 items →

Reverse percent: the 80% is the new amount, so the original is new ÷ 0.8. Students find an original from a changed amount, work profit/loss, discount, and tax, and use simple interest I = Prt and A = P(1 + rt).

Specification · for a parent or teacher

Part no.: percent-simple-interest
Course: Advanced Math 7 · Unit 7
Realm: Applied
Difficulty: 3 of 4 — Grade 6–7 core. Multi-step, first symbolic work.
Qty: 5 items

Part no. is the node's id; the realm is the kind of math; qty is how many practice items it carries.

Students can

find the original given the new amount; profit/loss, discount, tax; $I=Prt$ , $A=P(1+rt)$ .

Ready when

reverse-percent to $80 after 20% off ($100), and $I$ for $P=500$ , $r=4\%$ , $t=3$ years.

Formulas

Simple interest

I = Prt

Amount

A = P(1 + rt)

Watch for

“price after 20% off is $80, original?” answered $96$ (they took 20% of 80).

Before · requires

Percent and percent changepercent-change · Math 6
Simple equations in one variablelinear-equations-7 · Math 7

After · used by

Exponential functionsexponential-growth-decay · Math 1

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