Answer: 1.
- A 1
- B 3
- C 7
- D 9
Correct answer: A. 1
Explanation: Powers of 7 cycle with last digits 7, 9, 3, 1 (period 4). Since 100 is a multiple of 4, the last digit is 1.
Row n of Pascal's triangle gives the coefficients nC0, nC1, ..., nCn for the expansion of (a+b)ⁿ; each number is the sum of the two numbers diagonally above it, a direct visual proof of the identity nCr = (n-1)C(r-1) + (n-1)Cr.
Concept context
Expansion of (a+b) n , general term, middle term, binomial coefficients, and greatest term