Singapore Math · Field Guide
DIMENSIONS MATH 4A

First half

  • Numbers through 1 million
  • Addition/subtraction and mental methods
  • Multiples and factors
  • Multiplication and division
  • Fractions, mixed numbers, unlike fractions
  • Fraction multiplied by a whole number
  • Line graphs and line plots
DIMENSIONS MATH 4B

Second half

  • Measurements involving fractions
  • Area and perimeter
  • Decimal place value and decimal arithmetic
  • Angles, parallel and perpendicular lines
  • Shapes, cuboids and nets

4A · Numbers through 1,000,000

Understand the relationships between ones, tens, hundreds, thousands, ten-thousands, hundred-thousands, and millions. Use expanded form, benchmarks, number lines and rounding. Do not let correct rounding conceal a lack of place-value understanding.

4A · Factors and multiples

Concept Example / definition
Factor 12 has factors 1, 2, 3, 4, 6, 12
Multiple Multiples of 6 include 6, 12, 18, 24, …
Prime Exactly two distinct positive factors, e.g. 2, 3, 5, 7
Composite More than two positive factors, e.g. 4, 6, 8, 9
Common factors Of 12 and 18: 1, 2, 3, 6
Common multiples Of 4 and 6: 12, 24, 36, …

Useful divisibility patterns: multiples of 2 end in an even digit; multiples of 5 end in 0 or 5; multiples of 3 have digit sums divisible by 3; multiples of 9 have digit sums divisible by 9.

4A · Multidigit multiplication and division

The area model for 34 × 26

Write 34 as 30 + 4 and 26 as 20 + 6. The four rectangular regions are four partial products.

30 4
20 600 80
6 180 24
600 + 80 + 180 + 24 = 884

Place-value division

936 ÷ 4 = (800 + 120 + 16) ÷ 4 = 234

Check: 234 × 4 = 936. Students may use the standard algorithm after understanding its place-value meaning.

4A · Mixed numbers and fraction operations

A proper fraction is less than one; an improper fraction is at least one. A mixed number combines a whole number and a proper fraction.

Skill Method
Improper to mixed 11/4 = 2 3/4
Mixed to improper 3 2/5 = (3 × 5 + 2)/5 = 17/5
Unlike-denominator addition 3/4 + 2/5 = 15/20 + 8/20 = 1 3/20
Regroup a whole 3 1/4 = 2 5/4 = 2 10/8
Mixed-number subtraction 3 1/4 − 1 5/8 = 2 10/8 − 1 5/8 = 1 5/8
Fraction × whole number 3/4 of 28 = (28 ÷ 4) × 3 = 21

Teaching connection: Renaming a fraction or mixed number must preserve its value. This is why common denominators work and why the extra eighths in a regrouping step are not “created.”

4B · Decimals as fractions of ten and one hundred

Decimal Meaning
0.7 7/10
0.35 35/100
4.73 4 + 7/10 + 3/100
0.4 and 0.35 0.40 > 0.35

Add & subtract

2.70 + 0.85 = 3.55
3.40 − 1.76 = 1.64

Align place values, not just decimal punctuation.

Multiply/divide by wholes

2.35 × 4 = 9.40
8.4 ÷ 4 = 2.1

Think in hundredths or tenths to justify the computation.

4B · Measurement, geometry, and angles

Angle Measurement
Acute Between 0° and 90°
Right Exactly 90°
Obtuse Between 90° and 180°
Straight 180°
Reflex Between 180° and 360°
Full rotation 360°

An angle on a straight line is 180°; angles around a point sum to 360°. Also practice parallel/perpendicular lines, quadrilaterals, symmetry, and spatial reasoning about cuboids and nets. A cuboid has 6 faces, 12 edges, 8 vertices.

4B · Extended bar models

Multiplicative comparison

Sarah has three times John's stickers; together they have 72.

1 + 3 = 4 units; 72 ÷ 4 = 18

John has 18, Sarah has 54. The diagram and the equation x + 3x = 72 express the same relationship.

Grade 4 exit checklist

  • Accurate multidigit multiplication/division with explanations and estimates.
  • Factors, multiples, and common relationships.
  • Mixed numbers and unlike-denominator fraction operations.
  • Fractions of whole-number quantities.
  • Decimal comparison, hundredths, and the operations taught in Grade 4.
  • Area/perimeter, angles, and cuboid geometry.
  • Independent multistep bar-model or algebraic reasoning.