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Match List-I with List-II

List-IList-II
(A) Unit's digit of 2112^{11}(I) 2
(B) Unit's digits of 1113211^{132}(II) 1
(C) Remainder when 71×73×7571 \times 73 \times 75 is divided by 23(III) 4
(D) Remainder when 7307^{30} is divided by 5(IV) 8

Choose the correct answer from the options given below:

Solution

Correct Option: 2

Powers of 2 follow a repeating pattern for unit digits:

21=22^1 = 2 (unit digit: 2)

22=42^2 = 4 (unit digit: 4)

23=82^3 = 8 (unit digit: 8)

24=162^4 = 16 (unit digit: 6)

25=322^5 = 32 (unit digit: 2)

The pattern {2, 4, 8, 6} repeats every 4 powers.

To find the unit digit of 2112^{11}:

11÷4=211 \div 4 = 2 remainder 33

The remainder indicates position 3 in the pattern, which is 8.

(A) matches with (IV) = 8


Any power of 11 always ends in 1:

111=1111^1 = 11 (ends in 1)

112=12111^2 = 121 (ends in 1)

113=133111^3 = 1331 (ends in 1)

This occurs because 11×1=...111 \times 1 = ...1 always.

Therefore, 1113211^{132} has unit digit 1.

(B) matches with (II) = 1


Using modular arithmetic, find what each number leaves when divided by 23:

71÷23=371 \div 23 = 3 remainder 22, so 712(mod23)71 \equiv 2 \pmod{23}

73÷23=373 \div 23 = 3 remainder 44, so 734(mod23)73 \equiv 4 \pmod{23}

75÷23=375 \div 23 = 3 remainder 66, so 756(mod23)75 \equiv 6 \pmod{23}

Multiply the remainders:

2×4×6=482 \times 4 \times 6 = 48

Divide 48 by 23:

48÷23=248 \div 23 = 2 remainder 22

(C) matches with (I) = 2


Find the pattern of powers of 7 modulo 5:

71=77^1 = 7, remainder when divided by 5 is 22

72=497^2 = 49, remainder when divided by 5 is 44

73=3437^3 = 343, remainder when divided by 5 is 33

74=24017^4 = 2401, remainder when divided by 5 is 11

757^5 has remainder 22 (pattern repeats)

The pattern {2, 4, 3, 1} repeats every 4 powers.

To find remainder for 7307^{30}:

30÷4=730 \div 4 = 7 remainder 22

Position 2 in the pattern corresponds to 4.

(D) matches with (III) = 4


Final matching:

(A) → (IV) 8

(B) → (II) 1

(C) → (I) 2

(D) → (III) 4

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