pqhai wrote:

My 20 seconds approach. Hope it helps.

When see questions about square/square root, think about "last digit" approach. It helps you save a lot of time.

Last digit of 324 = 4. Sqrt of 4 is 2.

Last digit of 289 = 9. Sqrt of 9 is 3

Last digit of the sum MUST be 5 (2+3 = 5). Only D is correct.

You don't need to figure out what sqrt of 324 or sqrt of 289 are.

Hope it helps.

I'm not sure that this is completely right approach.

For example we have numbers 81 and 25

Last digit of 81 = 1. Sqrt of 1 is 1

Last digit of 25 = 5. Sqrt of 5 is 5

Last digit of sum should be 1 + 5 = 6

But sum of roots is 9 + 5 = 14

Or we can take numbers 576 and 144

Last digit of 576 = 6. Sqrt of 6 is 6

Last digit of 144 = 4. Sqrt of 4 is 2

Last digit of sum should be 6 + 2 = 8

But sum of roots is 24 + 12 = 36

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Simple way to always control time during the quant part.

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