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Binomial Theorem question

2022 · 28 Jul · Shift 1 · Q33
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  5. /2022 · 28 Jul · Shift 1 · Q33

Binomial Theorem question

2022 · 28 Jul · Shift 1 · Q33

JEE MainMathematicsBinomial TheoremMCQ+4 / −1
The remainder when 72022+320227^{2022}+3^{2022}72022+32022 is divided by 5 is :
  1. A
    0
  2. B
    2
  3. C
    3
  4. D
    4
View written solutionFree

Correct answer: C

  1. We need the remainder when 72022+320227^{2022}+3^{2022}72022+32022 is divided by 555.

So we work modulo 555.

  1. Reduce the bases modulo 555: 7≡2(mod5)7 \equiv 2 \pmod{5}7≡2(mod5) So, 72022≡22022(mod5)7^{2022} \equiv 2^{2022} \pmod{5}72022≡22022(mod5)

Also, 32022≡32022(mod5)3^{2022} \equiv 3^{2022} \pmod{5}32022≡32022(mod5)

Thus we need 22022+32022(mod5).2^{2022}+3^{2022} \pmod{5}.22022+32022(mod5).

  1. Find the pattern of powers modulo 555.

For 2n2^n2n modulo 555: 21≡22^1 \equiv 221≡2 22≡42^2 \equiv 422≡4 23≡8≡32^3 \equiv 8 \equiv 323≡8≡3 24≡16≡1(mod5)2^4 \equiv 16 \equiv 1 \pmod{5}24≡16≡1(mod5) So the cycle length is 444.

For 3n3^n3n modulo 555: 31≡33^1 \equiv 331≡3 32≡9≡43^2 \equiv 9 \equiv 432≡9≡4 33≡12≡23^3 \equiv 12 \equiv 233≡12≡2 34≡6≡1(mod5)3^4 \equiv 6 \equiv 1 \pmod{5}34≡6≡1(mod5) Again, the cycle length is 444.

  1. Now reduce the exponent 202220222022 modulo 444: 2022÷4=505 remainder 22022 \div 4 = 505 \text{ remainder } 22022÷4=505 remainder 2 So, 2022≡2(mod4).2022 \equiv 2 \pmod{4}.2022≡2(mod4).

Hence, 22022≡22≡4(mod5)2^{2022} \equiv 2^2 \equiv 4 \pmod{5}22022≡22≡4(mod5) and 32022≡32≡9≡4(mod5).3^{2022} \equiv 3^2 \equiv 9 \equiv 4 \pmod{5}.32022≡32≡9≡4(mod5).

  1. Add them: 22022+32022≡4+4=8≡3(mod5).2^{2022}+3^{2022} \equiv 4+4 = 8 \equiv 3 \pmod{5}.22022+32022≡4+4=8≡3(mod5).

Therefore, the remainder is 3.\boxed{3}.3​.

  1. Checking options:
  • A: 000 ❌
  • B: 222 ❌
  • C: 333 ✅
  • D: 444 ❌

So the correct option is C.

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