Long Multiplication: 90 × 90

"Long Multiplication Calculator" Calculator

Multiplicand (number to be multiplied)

Multiplier (number to multiply by)

What is 90 × 90?

Answer

90 × 90 = 8,100

90 × 90 is a square: a number multiplied by itself, so 8,100 is the square of 90. Below, 90 is multiplied by 90 in a column, digit by digit.

90 × 90 in a Column

The multiplicand goes on top, the multiplier underneath, both aligned on the right. Only one digit of the multiplier is not zero, and it stands for 90, so there is a single partial product and the answer goes straight under the line.

   90
×  90
 8100
90 × 90 = 8,100

Step-by-Step Solution

Step 1: The last digit of the multiplier is 0, so this partial product is 0 and adds nothing to the total.

Step 2: The next digit of the multiplier is 9, and it stands for 90: 90 × 90 = 8,100.

  • 0 × 9 = 0. Write 0.
  • 9 × 9 = 81. Write 1 and carry 8.
  • No digits are left, so the carried 8 is written in front: the partial product is 810.

90 × 90

=

8,100

Check It, and What It Is Not

Check by dividing back. Multiplication and division undo each other, so 8,100 ÷ 90 = 90 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.

90 × 90 is a number, not an area. If those are the sides of a room in feet, the answer is 8,100 square feet — the same arithmetic, a different question, and it is answered by the square footage calculator.

See Also

About "Long Multiplication Calculator" Calculator

This calculator multiplies two whole numbers the way it is done on paper: digit by digit, carrying where the column overflows, then adding the partial products together. For example, it can help you find out what is 90 × 90? (The answer is: 8,100). Enter the multiplicand (e.g. '90') and the multiplier (e.g. '90') and hit the button. The order of the two numbers never matters: swapping the factors leaves the product unchanged, so either one can go on top. Fractions and mixed numbers belong to the fraction multiplication calculator, and the reverse operation is long division.

"Long Multiplication Calculator" Calculator

Multiplicand (number to be multiplied)

Multiplier (number to multiply by)

Products of 90

MultiplicationProduct
90 × 4360
90 × 5450
90 × 6540
90 × 7630
90 × 8720
90 × 9810
90 × 10900
90 × 11990
90 × 121,080
90 × 151,350
90 × 161,440
90 × 201,800
90 × 252,250
90 × 302,700
90 × 403,600
90 × 504,500
90 × 605,400
90 × 756,750
90 × 807,200
90 × 908,100

FAQ

What is 90 × 90?

90 × 90 = 8,100

Is 8,100 a square number?

Yes. 90 × 90 = 8,100, so 8,100 is the square of 90. A square is simply a number multiplied by itself, which is why both factors here are the same.

How do you check that 90 × 90 = 8,100?

Divide the product back by one of the factors: 8,100 ÷ 90 = 90 exactly, with no remainder. Multiplication and division undo each other, which is what makes this check work.

What are the partial products of 90 × 90?

Only one of them counts: every other digit of 90 is a zero and contributes nothing, so the work comes down to 90 × 90 = 8,100, with nothing left to add.

See Also