Which is not a triangular number?
10         b. 15       c. 6        d. 12
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Maybe 10

Because

5*3=15

2*3=6

4*3=12

it's 10. ten cannot be divided into 3 with whole number answer. 10 cannot be a triangular number that can be divided by 3

b) 1/3 * 1/5

step-by-step explanation:

each smallest part is 1/15 since the written one is 1/5 and it's divided by 3 equal parts. (1/5 )/3 = 1/15 = 1/3 * 1/5

a triangular prism is a 3 dimensional shape composed of triangles and rectangles. it is made from two triangular bases and three rectangular sides.