4 sticks = 1 x 4
10 sticks = 2 x 5
18 sticks = 3 x 6

5th figure = 5 x 8 = 40

70 sticks = 7 x 10

Figure 7 has 70 sticks

But how did you get 7×10

Simple. Number of sticks is always figure number x (figure number + 3)

The only 2 whole numbers that can give a product of 70 , and where the figure number is 3 less than the other number, is 7 and 10

Alternatively,

Position 1 : 4

Position 2 :4 + 6 = 10

Position 3 :10 + 8 = 18

The increase to the next figure is always two more than the previous increase.



Now 4+6+8+10+12+14+16 = 70

Increasing by 6 times using this pattern gets you to 70 sticks.

From figure 1, you reach position 7 .