Quantitative Aptitude questions answering in Eliminating method

Question    ?² +79² = 172² - 88² - 8203. Find?

                   a) 86   b) 89 c) 83 c) 93

If you are following the conventional method it will take around 2 minutes.

Here we are using the smart eliminating method.ie eliminating the wrong answers from the 4 options. This is done by the follow the unit digit method. We are taking the last digits of each numbers.

X + number ends in 9’s square is 1 = 2’s square is 4 – 8’s square is 4 – 3

X + 1 = 4-4-3

X + 1 = 0-3

X + 1 = 7

X = 6

From the above equation we can say  ? ² ends in 6, so the number? Is ends in either 4 or 6.

Let’s look at the four answer options, we can find that only option a :86 is ends in either 4 or 6.so we can eliminate all the other options and conclude the option a is the right answer