中一數學題目急 最佳40點

A few years ago, MR CHAN bought 10kg Tea A for $130 per kg and 2kg Tea B $600 per kg. Now he just sells all of the two types of tea for $400 and $2500 per kg respectively. On the whole, what is the profit percent?

Cost price
= $(130 x 10 + 600 x 2)
= $2500

Selling price
= $(400 x 10 + 2500 x 2)
= $9000

Profit per cent
= [(9000 - 2500)/2500] x 100%
= 260%



A model manufacturer made 4000 model aeroplanes and sold them at a profit of $780. If the profit per cent was 30%, find the cost price of each model aeroplane.

Cost price of each model aeroplane
= $780 ÷ 30% ÷ 4000
= $0.65



In a watch shop, all items are sold at a 30% discount and customers paying in cash can enjoy a further 5% discount on the reduced prices. If Cindy pays $1064 in cash to buy a watch, what is the marked price?

Marked price
= $1064 ÷ (1 - 5%) ÷ (1 - 30%)
= $1600



A computer game marked at $320 is sold at a discount of 40%. If the discount is 64% of the cost price, find the profit or loss per cent.

Cost price
= $320 x 40% ÷ 64%
= $200

Selling price
= $320 x (1 - 40%)
= $192

Loss per cent
= [(200 - 192)/200] x 100%
= 4%



Clement deposits a sum of money in bank for 146 days and the interest rate is 4% p.a. After 146 days, he received the amount of $25400. Find the original sum of money that he deposited.

Original sum of money
= $25400 ÷ [1 + 4% x (146/365)]
= $25000



Jacky borrows $40000 from a bank where simple interest is calculated at an interest rate of R% p.a. Find the value of R. The amount is 3 times the original principal after 20 years.

3P = P x (1 + R% x t)
2P = P x R% x t

R%
= (3 - 1) ÷ 20
= 10%

Hence, R = 10

A few years ago, MR CHAN bought 10kg Tea A for $130 per kg and 2kg Tea B $600 per kg. Now he just sells all of the two types of tea for $400 and $2500 per kg respectively. On the whole, what is the profit percent?

Cost price
= $(130 x 10 + 600 x 2)
= $2500

Selling price
= $(400 x 10 + 2500 x 2)
= $9000

Profit per cent
= [(9000 - 2500)/2500] x 100%
= 260%



A model manufacturer made 4000 model aeroplanes and sold them at a profit of $780. If the profit per cent was 30%, find the cost price of each model aeroplane.

Cost price of each model aeroplane
= $780 ÷ 30% ÷ 4000
= $0.65



In a watch shop, all items are sold at a 30% discount and customers paying in cash can enjoy a further 5% discount on the reduced prices. If Cindy pays $1064 in cash to buy a watch, what is the marked price?

Marked price
= $1064 ÷ (1 - 5%) ÷ (1 - 30%)
= $1600



A computer game marked at $320 is sold at a discount of 40%. If the discount is 64% of the cost price, find the profit or loss per cent.

Cost price
= $320 x 40% ÷ 64%
= $200

Selling price
= $320 x (1 - 40%)
= $192

Loss per cent
= [(200 - 192)/200] x 100%
= 4%



Clement deposits a sum of money in bank for 146 days and the interest rate is 4% p.a. After 146 days, he received the amount of $25400. Find the original sum of money that he deposited.

Original sum of money
= $25400 ÷ [1 + 4% x (146/365)]
= $25000



Jacky borrows $40000 from a bank where simple interest is calculated at an interest rate of R% p.a. Find the value of R. The amount is 3 times the original principal after 20 years.

3P = P x (1 + R% x t)
2P = P x R% x t

R%
= (3 - 1) ÷ 20
= 10%

Hence, R = 10