Decimals & Percents · Add & subtract decimals · 2.3

Decimals & money.

Money is decimals with two places (cents). Add and subtract amounts by lining up the points; answers are written with exactly two decimal places.

01 / THE IDEA

See it work.

Watch the method

Decimals & money

$12.50 + $3.75 = $16.25.

1 / 2
12.50+3.7512.50 + 3.75
1

Line up the decimal points

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

12.50+3.7512.50 + 3.75
2

Bring down the point

The point in the answer lines up too.

=16.25= 16.25
02 / YOUR TURN

Practice until it feels automatic.

Your turn

Work it out.

Type dollars, e.g. 12.50.

streak 0
best 0
… =$
— / WHY IT WORKS

The idea underneath.

Two places for cents

Dollars and cents are hundredths. Keep two decimal places in money answers.

Why it works

$12.50 + $3.75 = $16.25.

03 / WORKED EXAMPLES

From easy to tricky.

EX 1easy

Add 2.09 + 8.88

1

Line up the decimal points

Stack the numbers so the points align, then add column by column. 2.09 + 8.88

2

Bring down the point

The point in the answer lines up too. = 10.97

EX 2medium

Add 5.68 + 3.91

1

Line up the decimal points

Stack the numbers so the points align, then add column by column. 5.68 + 3.91

2

Bring down the point

The point in the answer lines up too. = 9.59

EX 3hard

Add 9.05 + 2.28

1

Line up the decimal points

Stack the numbers so the points align, then add column by column. 9.05 + 2.28

2

Bring down the point

The point in the answer lines up too. = 11.33

04 / COMMON TRAPS

Where students slip.

Trap

Dropping a trailing zero (writing $16.2).

Fix

Money keeps two places: $16.20.

Trap

Misaligning dollars and cents.

Fix

Line up the decimal points.

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

Add 1.44 + 0.75

Need a hint?
  • Keep two decimal places.
  • Line up the points.
C2

Add 3.64 + 2.27

Need a hint?
  • Keep two decimal places.
  • Line up the points.
C3

Add 5.65 + 8.21

Need a hint?
  • Keep two decimal places.
  • Line up the points.
C4

Add 9.92 + 3.63

Need a hint?
  • Keep two decimal places.
  • Line up the points.
Apply

Apply (4)

A1

Add 1.58 + 6.99

Need a hint?
  • Keep two decimal places.
  • Line up the points.
A2

Add 0.85 + 5.92

Need a hint?
  • Keep two decimal places.
  • Line up the points.
A3

Add 9.32 + 8.88

Need a hint?
  • Keep two decimal places.
  • Line up the points.
A4

Add 6.81 + 4.29

Need a hint?
  • Keep two decimal places.
  • Line up the points.
Extension

Extension (4)

E1

Add 2.32 + 5.28

Need a hint?
  • Keep two decimal places.
  • Line up the points.
E2

Add 0.68 + 0.48

Need a hint?
  • Keep two decimal places.
  • Line up the points.
E3

Add 8.79 + 2.16

Need a hint?
  • Keep two decimal places.
  • Line up the points.
E4

Add 3.06 + 4.12

Need a hint?
  • Keep two decimal places.
  • Line up the points.