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Estimate √50

Step by step, with the reason for every step · Estimating square roots · Foundations

Step by step

The question

Question: estimate √50.

√50

The square root of 50 is the number that times itself makes 50.

√50 × √50 = 50

Careful!

The square root is not half.

25 times 25 is 625, far more than 50.

Careful: not √50 = 25 ✗

1 List the squares

First, the square numbers near 50.

6 times 6 is 36.

7 times 7 is 49.

8 times 8 is 64.

9 times 9 is 81.

2 Find where it fits

50 is between the squares 49 and 64.

= 49 < 50 < 64

A bigger number has a bigger square root.

So √50 is between √49 and √64.

= √49 < √50 < √64

√49 is 7.

√64 is 8.

So √50 is between 7 and 8.

= 7 < √50 < 8

3 Which is closer

50 is 1 more than 49, and 14 less than 64.

= 50 − 49 = 1, 64 − 50 = 14

1 is less.

So 50 is closer to 49, and √50 is closer to 7.

1 < 14: closer to 49

So √50 is between 7 and 8, closer to 7.

= 7 < √50 < 8, closer to 7

4 Check

Let's check with the number halfway: 7.5.

7.5 times 7.5 is 56.25, more than 50.

7.5 × 7.5 = 56.25 > 50

So √50 is below 7.5: closer to 7.

The answer is right!

√50 < 7.5: closer to 7

Let's look back.

First: list the squares.

Then: find where it fits.

Then: which is closer.

Last: check.

Answer
= 7 < √50 < 8, closer to 7

Your turn

Try this one yourself, then check:

Estimate √52
Show the answer
7 < √52 < 8, closer to 7

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