To find the precent of something you multiply it by 1/100th of what precentage youre trying to find. That's a really weird way of explaining it... It's easier to show with examples.
Some numbers you probably know off the top of your head (whats 100% of 5 or 50% of 20?) But you can also move the decimal place over twice. 100 becomes 1.00 and 1x5 is 5. Same with 50%, it turns into 0.50 or 0.5. and 0.5x20 is 10...
0.25 x 80 is 20 so 25% of 80 is 20
0.8 x 125 is 100 so 80% of 125 is 100
0.6 x 120 is 72 so 60% of 120 is 72
0.45 x 15 is 6.75 so 45% of 15 is 6.75
0.5 times 60 is 30 so 50% of 60 is 30
and for the shopkeeper
0.46 x 150 is 69 so he sold 69 newspapers (nice)
0.24 x 150 is 36 so he sold 36 pens
0.12 x 150 is 18 so he sold 18 books
and 0.18 x 150 is 27 so he sold 27 "other items"
we can check this by adding together the items sold
69+36+18+27=150
(this only works if they gave us 100% of the items sold)
