Lily 發問於 科學及數學數學 · 8 年前

# Maths急救!!!!!!!!!!!!!

1. Mrs Wong deposited a certain amount of money in a bank to earn interest. The total amount \$A she can obtain after t years is given by

A=10000(1+0.02t)

a) how much did Mrs Wong deposit at the beginning?

b) If Mrs Womg has deposited the money for at least two years, at least how much can she obtain from the bank?

c)At least how many years should Mrs Wong wait until she can obtain a total amount of \$12000 from the bank?

2. In each of the following, write down an inequality to show the range of values of y if x ≤ -4.

(a) y=2x-7 (b) y=8-3x/5 (c) y=-5/6(2+5x)

3. Dick wants to join a golf club. The Golden club membership costs \$350 per person and \$26 will be charged for each hour of playing time. The Silver club membership costs \$200 per person and \$40 will be charged for each hour of playing time. Let x be the number of hours that Dick plans to play.

(a) Express the amount Dick has to play, in terms of x, if he joins

(i) the Golden club membership,

(ii) the Silver club membership.

(b) At least how many hours should Dick play so that it costs less to join the Golden club membership than Silver Club membership?

4. A plant is 64 cm tall now, and it grows at rate of 20% per year.

(a) What will be its height 3 years later?

(b) What was its height 2 years ago?

5. A new car is worth \$250000 and its depreciation rate is 30% for the first year and 20% for every subsequent year.

(a) Find its value 3 years later.

(b) Find the overall percentage change in its value over these 3 years.

6. A sum of \$5000 is deposited in a bank at 8% p.a. for 2 years. Find the interests if it is

(a) calculated on simple interest,

(b) compounded yearly.

7. Jack deposits \$80000 in a bank at 6% p.a. for 1 year. Find the amount obtained if the interest is compounded

(a) quarterly, (b) monthly.

### 1 個解答

• 8 年前
最愛解答

1a

When she deposits at the beginning, t=0

A=10000(1+0.02*0)

A=10000

1b

t=2

A=10000(1+0.02*2)

A=10400

She obtain at least\$10400 from the bank

1c

A=12000

12000=10000(1+0.02*t)

1.2=1+0.02*t

t=10

Mrs Wong should wait at least 10years until she can obtain a total amount of \$12000 from the bank

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2 x ≤ -4 (given)

a) y=2x-7

1/2(y+7) =x

so 1/2(y+7)≤-4

y≤1

b) y=(8-3x)/5

x=(8-5y)/3

so (8-5y)/3 ≤ -4

20≤ 5y

4≤y

c) y=-5/6(2+5x)

6y= -10-25x

x= (-6y-10)/25

so (-6y-10)/25 ≤ -4

6y+10≤ 100

y≤ 15

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資料來源： me