Decimals & Percents · Capstone · C1

Pick the right move.

The last skill is choosing: line up the points to add or subtract, count places to multiply, shift points to divide, convert between decimal/percent/fraction, and apply a percent (of a number, discount, tax, change).

01 / THE IDEA

See it work.

Watch the method

Pick the right move

Read the problem, then pick decimals or percents and the right move.

1 / 2
0.2×0.30.2 \times 0.3
1

Multiply ignoring the points

Multiply as whole numbers first.

0.2×0.30.2 \times 0.3
2

Count the decimal places

1 + 1 = 2 decimal place(s) in the answer.

=0.06= 0.06
02 / YOUR TURN

Practice until it feels automatic.

Your turn

Work it out.

Type a decimal, e.g. 0.75.

streak 0
best 0
… =
— / WHY IT WORKS

The idea underneath.

The decision

Add/subtract → line up points. Multiply → count places. Divide → shift points. Percent → convert and multiply, then add/subtract for change.

Why it works

Identify the operation first.

03 / WORKED EXAMPLES

From easy to tricky.

EX 1easy

Solve 4.21 + 9.21

1

Line up the decimal points

Stack the numbers so the points align, then add column by column. 4.21 + 9.21

2

Bring down the point

The point in the answer lines up too. = 13.42

EX 2medium

Solve 0.6

1

Multiply by 100

Percent means “out of 100”, so ×100 — shift the point two places right. 0.6 × 100

2

Add the % sign

The result is the percent. = 60%

EX 3hard

Solve 0.05

1

Multiply by 100

Percent means “out of 100”, so ×100 — shift the point two places right. 0.05 × 100

2

Add the % sign

The result is the percent. = 5%

04 / COMMON TRAPS

Where students slip.

Trap

Using the wrong operation’s rule.

Fix

Match the rule to the operation.

Trap

Skipping the size check.

Fix

Estimate to catch a misplaced point.

05 / QUIZ

Test yourself.

The Test

12 problems across three tiers. Auto-graded on submit. Hints and a full walkthrough on every question. Your work is saved on this device — sign in to keep it across devices.

0/12Answered
How to answerType just the value. Formatting won't trip you up — we ignore spaces, capital letters, commas, and subscript style, so t₁ = 5, d = 3 and t1=5,d=3 both count. For a list of numbers, separate them with commas (e.g. 3, 10, 17).
Core

Core (4)

C1

Solve 100 to the nearest 50%

Need a hint?
  • Identify what’s being asked.
  • Apply the matching method; check the size.
C2

Solve 150 to the nearest 50%

Need a hint?
  • Identify what’s being asked.
  • Apply the matching method; check the size.
C3

Solve 5% of 180

Need a hint?
  • Identify what’s being asked.
  • Apply the matching method; check the size.
C4

Solve 60% of 200

Need a hint?
  • Identify what’s being asked.
  • Apply the matching method; check the size.
Apply

Apply (4)

A1

Solve 0.125

Need a hint?
  • Identify what’s being asked.
  • Apply the matching method; check the size.
A2

Solve 180 to the nearest 25%

Need a hint?
  • Identify what’s being asked.
  • Apply the matching method; check the size.
A3

Solve 0.1 × 0.3

Need a hint?
  • Identify what’s being asked.
  • Apply the matching method; check the size.
A4

Solve 0.9 × 0.7

Need a hint?
  • Identify what’s being asked.
  • Apply the matching method; check the size.
Extension

Extension (4)

E1

Solve 20% of 190

Need a hint?
  • Identify what’s being asked.
  • Apply the matching method; check the size.
E2

Solve 0.25

Need a hint?
  • Identify what’s being asked.
  • Apply the matching method; check the size.
E3

Solve 120 to the nearest 20%

Need a hint?
  • Identify what’s being asked.
  • Apply the matching method; check the size.
E4

Solve 0.25

Need a hint?
  • Identify what’s being asked.
  • Apply the matching method; check the size.