Take 15. Multiply that by itself, then multiply the product by itself and proceed until you have thus multiplied 15 products in turn. - It has been said that it will take twenty-five years to solve this problem.

"If a goose weighs ten pounds and half its own weight, what is the weight of the goose ?"

"A snail climbing up a post twenty feet high ascends five feet every day and slips down four feet every night; how long will the snail take to reach the top of the post?"

'A wise man having a window one yard high and one yard wide, requiring more light, enlarged his window to twice its former size; yet the window was still only one yard high and one yard wide. How was this done?"

All the products of nine in the multiplication come to nine. Try it.

' 'Take any row of figures, and reversing their order, make a subtraction" of the latter from the former, "add up the digits of the remainder and the result will be nine."