alleryStart learning →Dots are stacked as 1, 3, 6, 10, 15 in successive layers. How many in the next stack?
A19
B20
C22
D21
Answer & Solution
Correct answer: D. 21
The gaps grow 2, 3, 4, 5, so the next gap is 6 and 15 + 6 = 21.
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