Cogito
Grade 7 Math · Chapter 3 · Lesson 2
Tax, Tips, and Markup
Adding a percent on top.
10 problems · about 18 minutes · 7.RP.A.3
What this lesson teaches
The child solves problems where a percent is added to an original amount.
- A tip, a tax, and a markup are all a percent of the original added on.
- Adding p% means multiplying by 1 + p/100.
- The multiplier does it in one step and can be undone later.
Warm-Up Review
From earlier lessons. Loosen up before the new work.
3 problemsReview — Percent Increase and Decrease: A 120 pound item falls 25%. New price?
Answer 90
Why 90 pounds.
Review — Unit Rates with Fractions: ⅖ mile in ⅕ hour. Miles per hour?
Answer 2
Why 2 mph.
Review — The Graph of a Proportional Relationship: Proportional graph through (4, 24). What is k?
Answer 6
Why k = 6.
Warm Up
Straightforward practice. Get the method working first.
3 problems£90 with 20% added. Total in pounds?
Answer 108
Why £108.
£50 with 10% added. Total in pounds?
Answer 55
Why × 1.1.
£80 with 25% added. Total in pounds?
Answer 100
Why A quarter of 80 is 20.
Build It Up
The same ideas with more to keep track of.
2 problemsWhat multiplier adds 30%?
Answer 1.3
Why 100% + 30%.
£120 with 5% added. Total in pounds?
Answer 126
Why 5% of 120 is 6.
Stretch Yourself
Mixed problems. Work out what kind of question it is before you start.
2 problemsThe Bill: A £60 bill with a 10% tip. What is the total, in pounds?
Answer 66
Why £66.
The Tax: A £200 item with 20% tax added. What is the total, in pounds?
Answer 240
Why £240.