Long Multiplication: 21 × 2
What is 21 × 2?
Answer
21 × 2 and 2 × 21 are the same product — the order of the factors never changes the answer, only the working. Below, 21 is multiplied by 2 in a column, digit by digit.
21 × 2 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.
| 2 | 1 | |
| × | 2 | |
| 4 | 2 |
Step-by-Step Solution
Step 1: Multiply the multiplicand by the last digit of the multiplier, 2: 21 × 2 = 42.
- 1 × 2 = 2. Write 2.
- 2 × 2 = 4. Write 4.
21 × 2
=42
Check It, and What It Is Not
Check by dividing back. Multiplication and division undo each other, so 42 ÷ 2 = 21 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.
21 × 2 is a number, not an area. If those are the sides of a room in feet, the answer is 42 square feet — the same arithmetic, a different question, and it is answered by the square footage calculator.
Related Calculations
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/21--2">21 × 2 = 42 - Long Multiplication - Calculatio</a>