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Practice sheet · Law Path · Lens 1: Math

Interest & rates

Practice for The Math of Law: deadlines, interest, payday loans, court limits, probability, rates, trial delay, rent and statistics (pp.8–16), plus A1–A2 (pp.17–18). Not legal advice.
Warm-upCoreLevel Up
Name Date Time I spent
Remember

Simple interest I = P × r × t. Yearly rate of a 2-week fee = fee % × 26. Rate per 100,000 = count ÷ population × 100,000. Add months carefully, one at a time.

Alberta examples from the book: most civil claims start within 2 years; the Court of Justice hears claims up to $100,000; Jordan ceilings are 18 or 30 months. This is general information, not legal advice.

Warm-up

One step

Dates, interest and rates.
1

Deadline

A problem is discovered on June 20, 2026. Using the 2-year rule (p.8), about when is the deadline to start a claim?

2

Simple interest

What is the simple interest on $1,200 at 8% a year for 2½ years?

3

Court limit

How far over the $100,000 limit is a $130,000 claim? How far under is a $64,000 claim?

4

Rate

A made-up town of 15,000 people had 24 incidents. What is the rate per 100,000?

Core

Two or three steps

Show what each number is “of”.
5

Payday loan

Borrow $400 for 2 weeks at the $14 per $100 cap. What is the fee, and what do you repay? What yearly rate is that? A credit card at 20% a year would charge about how much for 2 weeks?

6

Base rate

Evidence matches 1 in 50 people in a city of 40,000 adults. How many match? If a second clue matches 1 in 8 of those, how many match both?

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Law Path · Unizon · PracticeInterest, rates & probability
7

Trial delay

Someone is charged on September 15, 2025, in provincial court. When is the 18-month Jordan ceiling? If the defence causes 3 months of delay?

8

Rent

Three roommates share $2,100 rent. What is an equal split? A split by room size 2 : 1 : 1? In Alberta a deposit can be at most one month’s rent: how much in total?

9

Change

A made-up court had 160 cases last year and 136 this year. What is the percent change?

10

Statistics

Of 300 made-up cases, 72% ended in a guilty plea and 18% at trial. How many of each? What percent ended another way?

Level Up

Equations

A1–A2 (pp.17–18).
11

Solve for hours

A made-up lawyer charges $175 an hour plus a $250 flat fee. Solve 175h + 250 = 1,475.

12

Two quotes

Quote A: $160 an hour plus $400. Quote B: $200 an hour plus $160. When are they equal, and at what cost?

13

Find the rate

A $1,500 debt grew by $180 of simple interest in 2 years. Solve 1,500 × r × 2 = 180.

14

Court board

A display board is 4 dm longer than it is wide, with an area of 96 dm². Solve w(w + 4) = 96.

Make your own problem

Your turn to be the law student

  1. Pick a rule from the book that uses numbers: a deadline, a limit or a rate.
  2. Write a question that uses it with made-up dates or amounts.
  3. Solve it, and say what a real lawyer would need to check.

My problem, and my worked answer:

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Law Path · Unizon · PracticeInterest, rates & probability

Try every problem first, then check here. Wrong answers are useful: find the step where your work and the key split apart.

The key never prints with Print my work or Print blank. Open it to get its own Print the answer key button.

Answer key

Worked solutions. General information, not legal advice. Fees, towns and courts are made-up unless the book cites them.

Warm-up
1
about June 20, 2028 Add 2 years. Real deadlines depend on the facts; there’s also a 10-year outer limit (p.8).
2
$240 1,200 × 0.08 × 2.5 = 240.
3
$30,000 over · $36,000 under 130,000 − 100,000 = 30,000; 100,000 − 64,000 = 36,000.
4
160 per 100,000 24 ÷ 15,000 × 100,000 = 160.
Core
5
$56 · $456 · 364% · ≈ $3.08 4 × $14 = $56. 14% × 26 = 364%. 400 × 0.20 × 2 ÷ 52 ≈ $3.08: about $52.92 less.
6
800 · 100 40,000 ÷ 50 = 800. 800 ÷ 8 = 100. A match alone points to many people: the base-rate trap (p.12).
7
March 15, 2027 · June 15, 2027 Add 18 months: September 2025 → March 2027. Defence delay doesn’t count: + 3 months.
8
$700 each · $1,050, $525, $525 · $2,100 2,100 ÷ 3 = 700. 4 parts: $525 a part. One month’s rent = $2,100.
9
−15% (136 − 160) ÷ 160 = −0.15.
10
216 · 54 · 10% 0.72 × 300 = 216; 0.18 × 300 = 54; 300 − 270 = 30 = 10%.
Level Up
11
7 hours 175h = 1,225 → h = 7.
12
6 hours · $1,360 160h + 400 = 200h + 160 → 240 = 40h → h = 6. 960 + 400 = 1,360.
13
6% r = 180 ÷ 3,000 = 0.06.
14
8 dm × 12 dm w² + 4w − 96 = 0 → (w + 12)(w − 8) = 0 → w = 8.
Make your own: count months one at a time, say what each percent is “of”, and remember: this is maths practice, not legal advice.
Law Practice · Law Path · Unizon · Not legal adviceAnswer key