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Udemy > mafs > Flashcards

mafs Flashcards

1
Q

Estimate
6.32 x 6.51
___________
0.5

A

1.Round each number to its nearest significant figure
2.Solve

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2
Q

There are 15 pencils in a pack and 40 pens in a box.How many packs of pencils and how many packs of pens would we need to buy to have the same amount of each?

A

1.Write the multiples of each number.
2.Find the first common one
3.find the multiplier for the original number to get that and you have how many packs u need to get

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3
Q

≥

A

greater than or equal to.

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4
Q

≤

A

Less than or equal to

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5
Q

<

A

Less than

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6
Q

>

A

Greater than

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7
Q

Do less than or equal to/greater than or equal to get a shaded circle on a number line?

A

Yes,Open circles are used for numbers that are less than or greater than (< or >). Closed circles are used for numbers that are less than or equal to and greater than or equal to (≤ or ≥).

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8
Q

A washing machine costs £640 plus 20% vat. John pays a £68 deposit and the rest in 10 equal monthly instalments.Work out the cost of each monthly payment?

A

1.Add Vat
10% of 640 = 64
20% of 640 = 128
640 + 128 = 768
2.Minus deposit
768-68 =700
3.work out monthly payments
700/10 = 70£pm

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9
Q

When plotting values on number lines when there is an inequality with an infinite value e.g. x ≥ 1 what would you draw on the number line?

A

You would draw an arrow showing the values.

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10
Q

A mobile phone is reduced by 20% in a sale.The sale price is £500
Work out the original price

A

We know that 500£ = 80% of the original price
500 / 80 = 6.25
6.25 = 1% of original price
6.25 x 100 = 625 = original price

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11
Q

A house rises in value by 3%.The value of the house increases by 7500£.Work out the value of the house before the increase.

A

7500 = 3%
2500 = 1%
2500 x 100 = 250,000£

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12
Q

Multiply these fractions
1/2 x 3/4 = 3/8

A

1.Multiply numerators
2.Multiply denominators

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13
Q

How do you divide fractions?

A

Dividing two fractions is the same as multiplying the first fraction by the reciprocal of the second fraction.

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14
Q

What is the difference between compond and simple interest?

A

Simple interest is calculated on the original (principal) amount, whereas compound interest is calculated on the original amount and on the interest already accumulated on it.

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15
Q

800£ is invested for 2 years offering a 1.5% simple interest rate per annum.
How much is in the account after 2 years

A

1.Find interest rate per year
10% of 800 = 80
1% of 800 = 8
.5% of 800 = 4
1.5% of 800 = 12
2.Work out interest for 2 years
12 x 2 = 24£
800 + 24 = 824

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16
Q

Emily invests 150,000£ in a savings account offering a compound interest rate of 2.4% per annum for 4 years.Work out the amount of interest Emily ears over 4 years?

A

1.Work out the multiplier
2.4% = 1.024
2.use formula
amount x multiplier ^ period
150,000 x 1.024^4
3.minus original amount from amount answer
164926.74 - 150,000 = 14926.74

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17
Q

What is the reciprocal of a fraction?

A

The reciprocal of a fraction is the numerator and denominator switched

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18
Q

What happens when you times a fraction by its reciprocal?

A

It will always be 1

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19
Q

Mary buys a car for 4000£.Each year it depreciates by 20%.Work out the value of the car after 3 years.

A

Y1
4000 x 0.8 = 3200
Y2
3200 x 0.8 = 2560
Y3
2560 x 0.8 = 2048
Or
4000 x 0.8^3 = 2048

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20
Q

In a bag 2/5 counters are blue.18 are blue. Work out the number of counters in a bag?

A

2/5 = 18
1/5 = 9
9 x 5 = 45
45 counters are in the bag

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21
Q

How to convert numbers into standard form?

A

1.count how many places the decimal would have to be moved for the number to be between.
1.1-9.9.
2.divide or times the number by 10 until its between 1.1-9.9
3.write the number x 10 ^ how many decimal places it moved

22
Q

Write 3^2 x 3^5 /3^3 as a power of three

A

m^f x m^u = m^f + u
m^z / m^l = m^ z - l
3^7 - 3^3 = 3^4
3^4 = 3x3x3x3

23
Q

5^-2

A

5^-2/1
reciprocal
1^2/5^2
1/25

24
Q

64^1/2

A

sq(64) = 8

25
Q

In a bike store there are 8 different bikes and 10 different choices of paint colour.How many different combinations are there?

A

8 x 10 = 80

26
Q

A three digit padlock uses the numbers from 0-9.How many of the possible three digit number combinations use three different digits?

A

10 different numbers for the first number
9 different numbers for the second number
8 different numbers for the third number
10 x 9 x 8 = 720
720 combinations

27
Q

6.4 has been rounded to the nearest decimal place write the error interval.

A

6.35≤x<6.45

28
Q

6.4 has been truncated to one decimal place.Write the error interval.

A

truncated means every other number before it has been “chopped of.
6.4≤x<6.5

29
Q

Simplify
30x^2,y^3/6x,y^2

A

5xy

30
Q

(2x^2y)^3

A

(d^i)^c = d ^ i x c
2^3 = 8
(x^2)^3= ( 2x3=6) = x^6
y^3 = y^3
8,x^6,y^3

31
Q

Expand
b(3b+7)

A

b x 3b = 3b^2
b x 7 = 7b
3b^2 + 7b

32
Q

Expand
3y(5-4y)

A

3y x 5 = 15y
3y x -4y = -12y^2

33
Q

Factorise
3x + 15

A

3(x + 5)

34
Q

Factorise
35x - 21x^2

A

7x(5 -3x)

35
Q

Factorise
x^2 + 7x + 12

A

(if the equation has a x^2, you write 2 double brackets with x)
(x )(x )
The pair of number will need to multiply to add the number without x
and add to make number with x
1.Write the factors pairs of 12
1 x 12
2 x 6
3 x 4
all multiply to make 12
1 + 12 = 13 X
2 + 6 = 8 X
3 + 4 = 7 so this one
then we write those 2 numbers in the brackets
(x + 3)(x + 4)
then expand it to make sure its correct

36
Q

Factorise
x^2 - 3x - 28

A

(x + 4)(x - 7)

37
Q

Solve
3x + 5 = 26

A

x = 7

38
Q

Solve
5x - 3 = 3x + 9

A

x = 6

39
Q

Make x the subject of
y = 3x + 5

A

Make x the subject means to make the equation x = bdwuh ed
y = 3x + 5
-5 from both sides
y - 5 = 3x
divide both sides by 3
y - 5 / 3 = x

40
Q

make the subject x
y = x / 3 + 5

A

minus 5 from both sides
y - 5 = x / 3
times each side by 3
3 y - 15 = x or
3(y - 5) = x

41
Q

Make x the subject
y = x + 5 / 3

A

times by 3
3y = x + 5
minus 5
3y - 5 = x

42
Q

a = 5b + 2c
b = 3 & c = -2

A

a = 5(3) + 2(-2)
15 + -4 = 11
a=11

43
Q

Solve the simultaneous equation
4x + y = 25
x -3y = 16

A

times the third equation by 3
12x + 3y = 75
x - 3y = 16
add numbers
13x = 91
divide both sides by 17
x = 7
to work out y substitute x into the equations.

44
Q

Adam, Brian & Chris are work colleagues. Adam is 8 yrs older than Chris.Brian is twice as old as Adam.
The sum of their ages is 92.

A

A:B:C
C + 8 = A
2A = B
B = 2(c + 8)
B = 2c + 16
C + C + 8 + 2C + 16 = 92
4C + 24 = 92
- 24 from both sides
4c = 68
c = 17

Chris = 17
Brian = 2(17 + 8) = 50
Adam = 25

45
Q

How do you work out the sum of interior angles in a polygon?

A

(n − 2 ) × 180
n is the number of sides in a polygon

46
Q

Solve
2x + 3 < 20

A

minus 3 from both sides
2x<17
x < 17/2 or 8.5

47
Q

Work out the nth term and the 50th term of this sequence?
3,7,11,15

A

4n-1
4(50) -1
199

48
Q

Find the nth term and will 84 be in this sequence?
6,11,16,21

A

5n +1

5n+1 = 84
5n = 83
n = 83/5 not whole number so No

49
Q
A
50
Q
A
51
Q
A
52
Q
A

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