Problem solving?

Question

My niece has got a math problem. It looks simple but I no math wiz. Need help.

Harry paid $7.80 for 3kg of sugar and 6kg of flour. If 1kg of sugar and 1kg of flour cost $1.50 find the cost of 1kg.

Sorry, it should be find out how much 1kg of flour cost.

Answer 1

Hope this helps

1kg of Sugar + 1Kg of flour =$1.5
Therefore 3kg of sugar + 3 kg of flour = $4.50

$7.80 - $4.50 = $3.30
$3.30/ 3kg of flour = $1.10 (is cost per kg of flour
3Kg of sugar + 6 * 1.1 = $7.80
Therefore $7.80 - (6 * 1.1) = 3 kg of sugar
$7.8 - $6.6 = 3 Kg of Sugar
$1.2 / 3 = $0.40 per kg of sugar
Cost per Kg
Sugar = $0.40 per kg
Flour = $1.10 per Kg
To prove the formula
(3 * 0.4)+ (6*1.1) = 7.8

Answer 2

I think that you need to edit your question. The wording of your question doesn't make sense. let me see if I can answer anyway.

If 1kg of sugar and 1 kg of flour both cost $1.50 why is it that you need to know what the cost of 1kg costs?

maybe,
If 1kg of sugar costs $1.50 then 3kg = $4.50. $7.80 - $4.50= $3.30, so $3.30/6kg = $0.55/kg

so, Flour = $0.55 per kg, Sugar $1.50 kg

$1.50 must have been the cost of a kg of sugar because $1.50 x 6 kg of flour = $9.00, more than the original cost.

Answer 3

Let

x = sugar

y = Flour

1.50 = cost of lkg

3x = the cost of sugar

6y = the cost of flour

7.80 = the combined cost

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x + y = 1.50 - - - - - - - Equation 1

3x + 6y = 7.80 - - - - - -Equation 2

- - - - - - - - - - - - - - - - - - -

Substitution Method equation 1

x + y = 1.50

x + y - x = 1.50 - x

y = 1.50 - x

Insert the y value into equation 2

- - - - - - - - - - - - - - - - - - - - - -

3x + 6Y = 7.80

3x + 6(1.50 - x) = 7.80

3x + 9.00 - 6x = 7.80

-3x + 9.00 = 7.80

- 3x + 9.00 - 9.00 = 7.80 - 9.00

- 3x = - 1.20

- 3x/-3 = - 1.20/-3

x = 0,4 The cost of sugar

The answer is x = 0.4

Insert the x value into equation 1

- - - - - - - - - - - - - - - - - - - - - - -

x + y = 1.50

0.4 + y = 1.50

0.4 + y - 0.4 = 1.50 - 0.4

y = 1.10 the cost of flour

The answer is y = 1.10

Insert the y value into equation 1

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Check for equation 1

x + y = 1.50

0.4 + 1.10 = 1.50

1.50 = 1.50

- - - - - - - - - - - - - - - - - - - - -

Check for equation 2

3x + 6y = 7.80

3(0.4) + 6(1.10) = 7.80

1.20 + 6.60 = 7.80

7.80 = 7.80

- - - - - - - - - - - - - - - - - - -

The cost of 1kg sugar equals $ 0.40

The cost of lkg of flour equals $ 1.10

- - - - - - - - - - - - - - - - - - - - - - - - -

The solution set is { 0.4, 1.10 }

- - - - - - - - -s

Answer 4

let s cents be the cost of 1 kg sugar and f centsbe the cost of 1kg flour
so 3s+6f = 780..eq a
& s+f = 150..eq b
multiply eq b by 3
3s+3f = 450..eq c
dedduct eq c from eq a
3f = 330 so f =110
substituting f = 110 in eq 1 s =40
so sugar costs 40 cents/kg and 1 kg flour costs $1.10 (110 cents)

Answer 5

1kg of sugar is 40c ; 1kg of flour is $1.10

solution:
3x + 6y = 7.80
x+y = 1.50 or 3x + 3y = 4.50

subtract these equations; we get y= 1.10 and x = 0.40

let me tell you that the question is to be edited first...

Answer 6

Let S represent the cost of 1 kg of sugar and F represent the cost of 1 kg of flour, the information given enables you to write two equations in two unknowns, which you can solve.

1) 3S + 6F = 7.80
2) 1S + 1F = 1.50

One approach is to modify equation 2 to state one unknown in terms of the other

S = 1.50 - F

and then substitute this result into equation 1

3(1.50 - F) + 6F = 7.80
4.50 - 3F + 6F = 7.80
3F = 3.30
F = 1.10

Use this in equation 2

S + F = 1.50
S + 1.10 = 1.50
S = .40

Time permitting, it is a good idea to check using the other equation

3S + 6F = 7.80
3(.40) + 6(1.10) = 7.80
1.20 + 6.60 = 7.80
7.80 = 7.80

Answer 7

First we find out how much 1kg of sugar & 2kg of flour cost.
So, $7.80 ÷ 3 = $2.60
Then we can find out how much 1kg of flour cost.
So, $2.60 - $1.50 = $1.10
The cost of 1kg of flour is $1.10.

Answer 8

If you set up the 2 equations and add them you get an answer. Flour is $1.10 per kg, and sugar is $.40 per kg.

3x + 6y = 7.80 (x is sugar cost, y is flour cost)
1x + 1y = 1.50

Multiply the bottom equation by (-3). It becomes -3x - 3y= -4.50

Add them together

3x + 6y = 7.80
+(-3x - 3y = -4.50)
________________
0x + 3y = 3.30
Solve for y (y=1.10)
plug it back in to one of the equations and solve for x (x= .40)

Answer 9

7.8=3X+6Y, so,

2.6=X+2Y, Also,
X+Y=1.5

subtract these 2 eqs,

Y=1.1
using X+Y=1.5, X=0.4

These are the costs of, X=1kg of sugar and, Y=1kg of flour

Answer 10

Let x=cost of 1 kg of sugar
y=cost of 1 kg of flour

Then,
3x +6y=7.80 . . . . 1
x + y = 1.50 . . . . 2

By multiplying eq. 2 by three we get

3(x + y) = 3(1.50)
3x + 3y = 4.50

Then, by elimination,

3x + 6y = 7.80
3x + 3y = 4.50
____________
3y = 3.30
y=1.10

Substitute on the eq. 2,

x + y = 1.50
x + 1.10 = 1.50
x = 0.40

Answer:
1 kg of sugar costs 40c and
1 kg of flour costs $1.10