Present ages of Rajeev and Anand are in the ratio of 7 10 respectively Five years hence the ratio of...........

Quantitative Aptitude (CSC) Problems based on Ages

Present ages of Rajeev and Anand are in the ratio of 7: 10 respectively. Five years hence, the ratio of their ages will become 8: 11 respectively. If the Sum of the present age of Rajeev and Anand is ab. then, find what the unit digit of (a^b) is?

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Explanation:

Let the present ages of Rajeev and Anand be 7x and 10x years respectively.
Then, (7x+5)/(10x+5)=8/11
77x+55=80x+40
3x=15
x=5
So, the present ages of Rajeev and Anand are (7×5) and (10×5) respectively.
The sum of their ages = (35+50)=85
Hence, a=8 and b=5
Then, ab=8⁵
We know unit digit of 8 repeated after 4 powers. So, unit digit 8⁵=8⁴8¹

unit digit on once's place8¹=>8