Decimals & Percents · Multiply decimals · 3.2

Decimal × decimal.

Multiply decimals as whole numbers, then count the total decimal places in both factors — the answer has that many. 0.2 × 0.3: 2 × 3 = 6, two decimal places → 0.06.

01 / THE IDEA

See it work.

Watch the method

Decimal × decimal

0.2 × 0.3 = 0.06 (1 + 1 = 2 places).

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.

Total the places

Decimal places in the answer = places in the first factor + places in the second.

Why it works

0.2 × 0.3 → 6 → 0.06.

03 / WORKED EXAMPLES

From easy to tricky.

EX 1easy

Multiply 0.4 × 0.2

1

Multiply ignoring the points

Multiply as whole numbers first. 0.4 × 0.2

2

Count the decimal places

1 + 1 = 2 decimal place(s) in the answer. = 0.08

EX 2medium

Multiply 0.1 × 0.4

1

Multiply ignoring the points

Multiply as whole numbers first. 0.1 × 0.4

2

Count the decimal places

1 + 1 = 2 decimal place(s) in the answer. = 0.04

EX 3hard

Multiply 0.9 × 0.5

1

Multiply ignoring the points

Multiply as whole numbers first. 0.9 × 0.5

2

Count the decimal places

1 + 1 = 2 decimal place(s) in the answer. = 0.45

04 / COMMON TRAPS

Where students slip.

Trap

Getting 0.6 instead of 0.06.

Fix

Two decimal places total → 0.06.

Trap

Counting the places wrong.

Fix

Add the places from BOTH factors.

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

Multiply 0.1 × 0.5

Need a hint?
  • Multiply ignoring the points.
  • Count the total decimal places.
C2

Multiply 0.9 × 0.3

Need a hint?
  • Multiply ignoring the points.
  • Count the total decimal places.
C3

Multiply 0.8 × 0.6

Need a hint?
  • Multiply ignoring the points.
  • Count the total decimal places.
C4

Multiply 0.9 × 0.7

Need a hint?
  • Multiply ignoring the points.
  • Count the total decimal places.
Apply

Apply (4)

A1

Multiply 0.4 × 0.1

Need a hint?
  • Multiply ignoring the points.
  • Count the total decimal places.
A2

Multiply 0.5 × 0.2

Need a hint?
  • Multiply ignoring the points.
  • Count the total decimal places.
A3

Multiply 0.9 × 0.6

Need a hint?
  • Multiply ignoring the points.
  • Count the total decimal places.
A4

Multiply 0.3 × 0.1

Need a hint?
  • Multiply ignoring the points.
  • Count the total decimal places.
Extension

Extension (4)

E1

Multiply 0.3 × 0.4

Need a hint?
  • Multiply ignoring the points.
  • Count the total decimal places.
E2

Multiply 0.9 × 0.7

Need a hint?
  • Multiply ignoring the points.
  • Count the total decimal places.
E3

Multiply 0.5 × 0.5

Need a hint?
  • Multiply ignoring the points.
  • Count the total decimal places.
E4

Multiply 0.3 × 0.9

Need a hint?
  • Multiply ignoring the points.
  • Count the total decimal places.