mathe~~S.1

A wire of 72cm long is bent into a rectangle.If the lenght of the rectangle is 19cm,find the width of the rectangle.

Let x cm be the width of the rectangle,
2(x + 19) = 72
x + 19 = 36
x = 17
Hence the width of the rectangle is 17cm.


In a school,50% of the girl wear glasses while 280 of boys wear glasses.If the number of girls wearing glasses is 2/7 of the number of boys,find the number of girls.

Let x be the number of girls,
(50%)x = (280)(2/7)
(1/2)x = 80
x = 160
Hence the number of girls is 160.


A shopkeeper raised the price of a table by 20%.Later he sold the table at a disconunt of 20%.How did the selling price compare with the original price?Use an example to explain.

Assume the original price of the table is $100,
Selling price
= $100 (1+20%) (1-20%)
= $100 (1.2) (0.8)
= $96
that is less than the original price by 4%.

141的因數：1, 3, 47, 141

Express each of the following numbers as a product of prime factors.

1.60= 2 × 2 × 3 × 5

2.252= 2 × 2 × 3 × 3 × 7

3.450= 2 × 3 × 3 × 5 × 5

4.729= 3 × 3 × 3 × 3 × 3 × 3

(72-19-19)/2 = 17