Cleave Books Puzzle Trio 3
7. 
It is possible to write down the digits 1 to 9 (writing each once and once only, and in order) and then place ordinary arithmetical signs as necessary so that the answer to the entire sum is 100.
For example 
1 × 2 + 34 + 56 + 7  8 + 9 = 100
and there several other ways it can be done. 
  Find a way that uses only + and  signs 
8. 
"How old are you?" "Well I forget exactly, but I do remember that my brother is two years older than I, … my sister is four years older than he, and … um, mother was twenty eight when I was born. … Oh, and my sister recently said that the average age of the four of us is seventyfour."
How old was he?

9. 
Kerry and Nick were going to cut the grass on their square lawn. They agreed that each should cut onehalf of the area.
Kerry went first and cut a border 2 metres wide all the way around.
After doing a few sums, Nicki agreed that exactly onehalf had been cut and happily cut the rest.
What was the area of the lawn? 
