Long Multiplication: 640 × 8
What is 640 × 8?
Answer
640 × 8 and 8 × 640 are the same product — the order of the factors never changes the answer, only the working. Below, 640 is multiplied by 8 in a column, digit by digit.
640 × 8 in a Column
The multiplicand goes on top, the multiplier underneath, both aligned on the right. The multiplier has a single digit, so there is one partial product and the answer goes straight under the line.
| 6 | 4 | 0 | ||
| × | 8 | |||
| 5 | 1 | 2 | 0 |
Step-by-Step Solution
Step 1: Multiply the multiplicand by the last digit of the multiplier, 8: 640 × 8 = 5,120.
- 0 × 8 = 0. Write 0.
- 4 × 8 = 32. Write 2 and carry 3.
- 6 × 8 = 48, plus the carried 3 makes 51. Write 1 and carry 5.
- No digits are left, so the carried 5 is written in front: the partial product is 5,120.
640 × 8
=5,120
Check It, and What It Is Not
Check by dividing back. Multiplication and division undo each other, so 5,120 ÷ 8 = 640 must come out exactly, with no remainder.
Fractions are a different calculation. Both factors here are whole numbers; for 2/3 or 2 3/4 use the fraction multiplication calculator, which multiplies numerators and denominators separately.
640 × 8 is a number, not an area. If those are the sides of a room in feet, the answer is 5,120 square feet — the same arithmetic, a different question, and it is answered by the square footage calculator.
See Also
- Long Division Calculator - Step-by-step long division with detailed explanation
- Multiplying Fractions Calculator - Multiply fractions, mixed numbers and whole numbers step by step
- Factors of a Number - List all Factors and Factor Pairs of a Number
- Greatest Common Factor - Find the Greatest Common Factor (GCF) of two numbers
- Least Common Multiple - Find the Least Common Multiple (LCM) of two numbers
<a href="https://calculat.io/en/number/long-multiplication/640--8">640 × 8 = 5,120 - Long Multiplication - Calculatio</a>