F.1 至F.2的MATHS 問題..(20點..)

以下有7條問題 希望大家可以寫埋條式比我

1. If the two adjacent sides of a square measure Xcm and (2X-3)cm respectively, find the perimeter of the square.

2.The cost of tea A is $30 per kg, the cost of tea B is $20per kg. If w kgof tea A and (w+1)kg of tea B are mixed together, and the cost of the
mixed tea is$24 per kg. Find w.

3.The electricity bill of Mary's family in August was $560. If in the next two consecutive months, the use of electricity is less than each previous month by 15%, find the electricity bill of Mary's family in October.(Give the answer correct to the nearst integer.)

4. Last month, there were 30 male students and 20 female students in the chess class. The no. of male students increases by r% and the
no. of female students are the same in this month, find r.

5.Two shops sell the smae brand of chocolate at the same price. Today they both cut down its price. Shop A lowers the price by 30%, and
increases by 30%after a week. Likewise, shop B lowers its price by 40%, and increases by 40% after a week . Are the prices of the chocolate at the two shops still the same after a week?

6. Find the distance between P(-4, -3)& Q(3, -3)

7. If the area of triangle PQR is 21 sq. units, and the coordinates of R are (4, k), find the two possible values of k.