Ankur Rupani (Imperial)
6 years ago
Lets move to question 8 A = 4^2m and B = 9^2n. Which of the following is the unit’s digit
Lets move to question 8
A = 4^2m and B = 9^2n.
Which of the following is the unit’s digit in A + B, if A andB are integers?
(A)5
(B)4
(C)9
(D)1
(E)7
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Momoh Mustapha
If m and n could be zeros (0) or fractions or positive integers, then the unit's digit in A+B could be anyone of the given options i.e. 4, 5, 9, 1, or 7 4: if e.g m = 0, n = ¼ 5: if e.g m = ½, n = ½; and m=1, n=½ 9: if e.g m=0, n=1 or 2; and m=5/2, n=¼ 1: if e.g m=½, n=½ 7: if e.g m=½, n=¼ Note that the possible powers used in my examples are not exhaustive. See more
Shiladitya Biswas
7, E
Shaishav Shah
@ankurrupani yeah.
Tejas S
E
Ankur Rupani (Imperial) Author
@ankurrupani very goos shaishav - yes m and n should have been given as positive integers as well :) good u caught that See more