Montana Math MT.7.RP.3
The Standard
Use proportional relationships to solve multi-step ratio and percent problems, including problems in context that involve simple interest, tax, markups and markdowns, gratuities and commissions, fees, percent increase and decrease, and percent error. This standard should incorporate cultural context relating to Montana Indigenous Peoples and local communities.
2026 Montana Mathematics Content Standards
Teacher's field guide
What This Standard Means
What Students Need to Do
- Students use ratios or equations to calculate percent changes and costs. They solve several steps in order, using the right amount for each rate, including interest, tax, tips, commissions, and percent error.
What Mastery Looks Like
- They show why an $80 item discounted 25%, then charged a $6 fee, costs $66. They use the accepted value, not their estimate, as the base for percent error.
Common Misconceptions
- Students add the rates of two successive changes as if both use the original price. They calculate simple interest on interest already earned, or divide percent error by the estimate instead of the accepted value.
How to Assess It
- An $80 bike repair is 25% off, then has a $6 parts fee. What is the final cost, and what percent below $80 is it?
Lesson moves
Ways to Teach It
Give pairs price tags for a mock book sale benefiting a Montana tribal language program; calculate 15% off $40, then add $6 shipping.
Have students explain why increasing $50 by 20% and then decreasing the result by 20% leaves $48, not $50.
Race in pairs to price a $200 loan after two years using 5% annual simple interest and a $3 fee.
Compare a $45 repair estimate with a $50 final bill on a mock local bike shop receipt; calculate percent error using $50 as the base.
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Printable MT.7.RP.3 Worksheet
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