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Match List-I with List-II

List-I (Statements/Expressions etc.)List-II (Values, etc.)
(A) Find the sum of the first 20 odd natural numbers.(I) 285
(B) How many prime numbers are there between 100 and 200?(II) 0
(C) Find the sum of the squares of the digits from 1 to 9.(III) 400
(D) Find the unit's digit in the product 81×82×83×.........×8981 \times 82 \times 83 \times ... ... ... \times 89?(IV) 21

Choose the correct answer from the options given below:

Solution

✅ Correct Option: 3

Sum of first nn odd numbers =n2=202=400= n^2 = 20^2 = 400. There are 21 primes between 100 and 200. Sum of squares 121^2 to 92=9⋅10⋅196=2859^2 = \frac{9\cdot10\cdot19}{6} = 285. The product 81×82×⋯×8981\times82\times\cdots\times89 contains 85 (a factor 5) and even numbers, so the unit digit is 0. Hence (A)-(III), (B)-(IV), (C)-(I), (D)-(II).

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