Answer:
16
Step-by-step explanation:
basic addition
ANSWER
C) 1, 3, 6, 10, 15, 21, 28, 36, 45
EXPLANATION
The recursive formula is,
when n is a natural number greater than 1.
When n=2,
when n=3,
when t=4,
When t=5,
when t=6,.
when t=7
When t=8,
When t=9,
Hence the first nine triangular number are
863.57 ×40/100 = 345.428
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i think the best estimate is answer b