Question

Express 21square as the sum of two consecutive numbers

Answer 1

Define x:

Let one number be x

The other consecutive number = x + 1

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Sum of 2 consecutive numbers = 21²:

x + (x + 1) = 21²

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Solve x:

x + (x + 1) = 21²

Open bracket and evaluate 21²:

x + x + 1 = 441

Combine like terms:

2x + 1 = 441

Take away 1 from both sides:

2x = 440

Divide both side by 2:

x = 220

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Find the two numbers:

one number = x = 220

the other number = x + 1 = 220 + 1 = 221

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Answer: The two numbers are 220 and 221.

Answer 2

21 sqare =441. Two consecutive numbers are
x+1 and x+2
x+1+x+2=441
2x+3=441
2x=441-3
2x=438
x=438÷2
x=219

x+1=219+1=220
x+2=219+2=221