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Find the number of perfect squares in the given series 2013, 2020, 2027,.

Find the number of perfect squares in the given series 2013, 2020, 2027,................, 2300  (Hint 44^2=1936)

a. 1  
b. 2   
c. 3  
d. Can’t be determined











Answer: a
Explanation:
The given series is an AP with common difference of 7. So the terms in the above series are in the form of 2013 + 7k.  We have to find the perfect squares in this format in the given series.
Given that 44^2 = 1936.
Shortcut: To find the next perfect square, add 45th odd number to 44^2.
So 45^2 = 1936 + (2 x 45 -1) = 2025
46^2 = 2025 + (2 x 46 - 1) = 2116
47^2 = 2116 + (2 x 47 - 1) = 2209
Now subtract 2013 from the above numbers and divide by 7. Only 2209 is in the format of 2013 + 7k.  One number satisfies.

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