A5. The steps are made of cubes. How many do we need if we want to make 9 steps?
(A) 40
(B) 42
(C) 45
(D) 48
(E) 50

![](https://cdn.mathpix.com/cropped/2024_06_07_c7870cece3ffb80afd9eg-2.jpg?height=189&width=197&top_left_y=2204&top_left_x=1720)
A5 For 9 steps, we need $(1+2+3+4+5+6+7+8+9)=45$ blocks.