a post is being driven in to the ground by a mechanical hammer. The distance it is driven by the first blow is 8 cm. Subsequently the distance it is driven by each blow is 9/10 of the distance it was driven by the previous blow.

The post if to be driven a total distance of at least 70 cm into the ground. Find the smallest number of blows needed to achieve this.

Question

a post is being driven in to the ground by a mechanical hammer. The distance it is driven by the first blow is 8 cm. Subsequently the distance it is driven by each blow is 9/10 of the distance it was driven by the previous blow. 

The post if to be driven a total distance of at least 70 cm into the ground. Find the smallest number of blows needed to achieve this.

anonymous · Answer

8+8*(|dw:1338434013159:dw|9/10)+8*(8/10)^2