RGS P1 Prelim 1997 Q20 (Simple question)
(i) Complete the number pattern
1 = 1
1 + 2 + 1 = 4
1 + 2 + 3 + 2 + 1 =
1 + 2 + 3 + 4 + 3 + 2 + 1 =
1 + 2 + 3 + 4 + 5 + 4 + 3 + 2 + 1 =
(ii) What sort of numbers do you get?
(iii) Find 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 7 + 6 + 5 + 4 + 3 + 2 + 1
(iv) How is your answer connected to the middle number?
(v) Write down the answer for 1 + 2 + 3..... 49 + 50 + 49 .... 3 + 2 + 1
(vi) If 1 + 2 + 3+ .... (k - 1) + k + (k - 1) ..... 3 + 2 + 1 = 196, find the value of k.
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Answer:
(i)
1 = 1
1 + 2 + 1 = 4
1 + 2 + 3 + 2 + 1 = 9
1 + 2 + 3 + 4 + 3 + 2 + 1 = 16
1 + 2 + 3 + 4 + 5 + 4 + 3 + 2 + 1 = 25
(ii) Squares
i.e. 12 = 1, 22 = 4, 32 = 9, 42 = 16, 52 = 25
(iii) 64
(iv) The answer is the square of the middle number, i.e. 82
(v) 502 = 2500
(vi) k2 = 196
Hence, k = 14