↧↧↧ Detailed Video Solution to the Problem ↧↧↧
We need to find the the remainder when 2^92 is divided by 7 ?Let's solve the problem using two Methods:Method 1: Cyclicity of Remainder of power of 2 by 7To solve this problem we need to find the cycle of remainder of power of 2 when divided by 7Remainder of \(2^1\) (=2) by 7 = 2
Remainder of \(2^2\) (=4) by 7 = 4
Remainder of \(2^3\) (=8) by 7 = 1
Remainder of \(2^4\) (=16) by 7 =
2 Remainder of \(2^5\) (=32) by 7 =
4Remainder of \(2^6\) (=64) by 7 =
1=> Cycle is 392 = 90 + 2 = Multiple of 3 + 2=> Remainder of 2^92 by 7 = Remainder of 2^2 by 7 =4Method 2: Binomial Theorem2^92 = 2^(90+2) = 2^90 * 2^2 = 2^(3*30) * 4 = 8^30 * 4
Remainder of 2^92 by 7 = Remainder of 8^30 by 7 * Remainder of 4 by 7 = (Remainder of 8^30) * 4Remainder of 8^30 = Remainder of (7 + 1)^30 by 7
Now, if we use Binomial Theorem to expand this then all the terms except the last term will be a multiple of 7
=> All terms except the last term will give remainder of 0 when divided by 7=> Problem is reduced to what is the remainder when the last term (i.e. 30C30 * 7^0 * 1^30) is divided by 7
=> Remainder of 1 * 1 * 1 is divided by 7
=> Remainder of 1 divided by 7 = 1
=> Remainder of 2^92 = (Remainder of 8^30) * 4 = 1 * 4 = 4
So,
Answer will be DHope it Helps!
Watch following video to MASTER Remainders by 2, 3, 5, 9, 10 and Binomial Theorem