[15分] Maths Questions (Percentage) 要列明步驟 =]

1. May attempted 18 multiple choice question which comprised 75% question of the test paper. What is the no. of question she didn't attempt?

Ans: Since 18 is only 75% of whole paper, the no of whole paper is 18/0.75 = 24.
Therefore, the no. of question she didn't attempt is 24-18 = 6

2. Ken takes 3hours 18mins to complete a race this year. The time he needed is 12% less than that in the last year. Find the time Ken needed to complete the race last year.

Ans: 3 hr 18 mins = 198 mins. The time he needed is 12% less which means only 88% of last year. So time he needed to complete the race last year is 198/0.88 = 225 min or 3 hrs and 45 mins. { or 198/ (1-0.12) also = 225 }

3. A game marked $280 is sold at 20%off. If the discount is 35% of its cost price, find the profit %.

Ans: If selling price is 280*(1-0.2) =224 and discount is 280-224=56. If 56 is 35% of cost price, then cost price is 56/0.35 =160. Therefore profit is selling price - cost = 224-160=64. Profit % is profit /cost = (64/160)*100%=40%

May attempted 18 multiple choice question which comprised 75% question of the test paper. What is the no. of question she didn't attempt?


18/(除)25%
=24questions


Ken takes 3hours 18mins to complete a race this year. The time he needed is 12% less than that in the last year. Find the time Ken needed to complete the race last year.


3hours 18mins=198mins

198minsx(100%+12%)
=221.76(mins)


A game marked $280 is sold at 20%off. If the discount is 35% of its cost price, find the profit %.

[280x(100%+20%)] x(100%-35%)
=226x(100%-35%)
=$218.4