AR008 · Arithmetic operations · Classes 4–7
Long multiplication
Long multiplication splits each number into tens and ones and multiplies every part. The area model shows the four partial products as rectangles.
23 × 14Long multiplication
📐 Formula
(10a + b)(10c + d) = 100ac + 10ad + 10bc + bd
✏️ Worked example
23 × 14 = 20 × 10 + 20 × 4 + 3 × 10 + 3 × 4 = 200 + 80 + 30 + 12 = 322.
🌍 Where it is used
Area of a room, cost of many items, totals in a stadium.
❓ Quick check
What is 12 × 15?
🏋️ Practice
Easy13 × 11 = ?
Answer: 143
MediumUse the area model for 32 × 21.
Answer: 600 + 30 + 40 + 2 = 672
ChallengeA hall has 48 rows of 36 seats. How many seats?
Answer: 1,728