1. Steven bought 400 apples at a total of $1000. Later he found that 10 of the apples have decayed. Then sold the remaining apples at $3 each. Find the profit / loss percentage of Steven if all the remaining apples were sold.
2. Charles's monthly salary is $8000. He used 60% of his salary on food and transportation, 25% on entertainment and he saves the remaining.
(a) Find the amount he saves each month.
(b) If his monthly salary is now increased by $500 and he saves them all, find the percentage of salary that he saves.
3. The cost of a music box is $450. The marked price is 20% higher than the cost. In order to increase the sales, the shopkeeper gives a 20% discount to all customers. What is the selling price of the music box?
4. There were totally 900 students in a secondary school last year. 45% of the students were boys and 60% of the boys wore glasses.
(a) Find the number of boys in the school who wore glasses last year.
(b) This year the total number of students in the school remains unchanged, but the percentage of boys is decreased by 5%. If the percentage of boys who wear glasses is increased by 10%, find the change in the number of boys who wear glasses in these two years.
中一數學題
2012-07-19 8:22 pm
回答 (2)
2012-07-20 1:57 am
✔ 最佳答案
1. 3 * (400-10)=1170(1170-1000)/1000 * 100%=17%
So the profit percentage is 17%.
2. (a) The amount he saves each month is:
$8000*(1-60%-25%)= $1200
(b) The percentage of salary that he saves is:
(1200+500)/8500 *100% =20%
3. The selling price of the music box is:
$450 *(1+20%) *(1-20%) =$432
4. (a) The number of boys in the school who wore glasses last year is:
900 *45% *60% =243
(b) The number of boys in the school who wear glasses this year is:
900 *(45%-5%) *(60%+10%) =252
So the change in the number of boys who wear glasses in these two years is:
252-243 =9 (indreased)
2012-07-19 8:41 pm
1. price of each apple= 1000/400=$2.5
decayed apple=$2.5 x 10 = $25
profit of remaining apple= 390 x $3 = $1170
profit percentage = $1170/$975 x 100% = 120%
2. a) 8000 x 15% = 1200
b) 1700/8500 = 20%
3. market price= 450 x 120% = $540
selling price= $540 x 80% = $432
4.a ) 900 x 45% x 60% = 243
b ) number of boys = 900 x 40% = 360
boys wear glasses= 360 x 70% = 252
change in number = 252-243 = 9
decayed apple=$2.5 x 10 = $25
profit of remaining apple= 390 x $3 = $1170
profit percentage = $1170/$975 x 100% = 120%
2. a) 8000 x 15% = 1200
b) 1700/8500 = 20%
3. market price= 450 x 120% = $540
selling price= $540 x 80% = $432
4.a ) 900 x 45% x 60% = 243
b ) number of boys = 900 x 40% = 360
boys wear glasses= 360 x 70% = 252
change in number = 252-243 = 9
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