Maths question- (easy?) ?!?

Question

Please tell me the answer and how to do it!

I'm desperate!

"On a ferry crossing, three cars and two caravans pay £405, and seven cars and three caravans pay £795. How much would five cars and four caravans pay?"

Answer 1

3C+2V=405
7C+3V=795
Multiply first by 3 and second by 2 Subtracting gives

5C =375
C= 75
V=90

So 5C + 4V = 735

Answer 2

These are two simultaneous equations which you need to solve by elimination firstly then the values for both are worked out to give the final answers, like this:-

C represents Cars and P represents caravans (as i couldn't find any other letter)

So, this question is the same as 'Solve these 2 equations simultaneously 3c+2p=405 and 7c+3p=795'

Multiply equation one by (3) and equation 2 by (2)
Which will bring us to: 9c+6p=1215 & 14c+6p=1590 as you see we have made both the 'p' terms the same (the same coefficient) (1)-(2) which leaves us with -5c+0=-375 now we just have the cs to find, so -375/-5 = 75, so c=75. Substitute the value of C in the original equation to find the value of P.
(3*75)+2p=405 = 225+2p=405. take away 225 from 405 to find the value of P. 2p=180 p=90. The original question states that we need to find how much 5 cars and 4 caravans will cost, for this we will use the values of C and p we have just found. (5*75)+(4*90)=735 , Here is a worked example mate! hope this helped.
~Ramadulla

Answer 3

x=cars
y=caravans

multiply by 3
3x + 2y = 405 > 9x + 6y = 1215
multiply by 2
7x + 3y = 795 > 14x + 6y = 1590

subtract 5x = 375
5x/5 = 375 x=75
so y = 90

Now, 5(75) + 4(90) = 375 + 360 = 735

Answer 4

x=cars
y=caravans

multiply by 3
3x + 2y = 405 > 9x + 6y = 1215
multiply by 2
7x + 3y = 795 > 14x + 6y = 1590

subtract 5x = 375
5x/5 = 375 x=75
so y = 90

Now, 5(75) + 4(90) = 375 + 360 = 735

Answer 5

x=cars
y=caravans

multiply by 3
3x + 2y = 405 > 9x + 6y = 1215
multiply by 2
7x + 3y = 795 > 14x + 6y = 1590

subtract 5x = 375
5x/5 = 375 x=75
so y = 90

Now, 5(75) + 4(90) = 375 + 360 = 735

Answer 6

3cars + 2caravans = £405
7cars + 3caravans = £795

Simpliest way
3 * (3cars + 2caravans = £405)
2 * (7cars + 3caravans = £795)

gives you
9cars + 6caravans = £1215
14cars + 6caravans = £1590

subract first equation from second
5cars = £375
1car = £75

substitute 1car into first equation
3(£75) + 2caravans = £405
£225 + 2caravans = £405
2caravans = £180
1caravan = £90

Therefore
5cars + 4caravans
5(£75) + 4(£90)
£375 + £360
£735

Answer 7

3 a + 2b = 405 => 9a + 6b = 1215
7a + 3b =795 => 14a + 6b = 1590

subtract 5a = 375
a = 75
b = 90

so 5a + 4b = 375 + 360 = 735

Answer 8

405 + 795
= 1200
1200 /14(number of objects)
= 85.71
85.71* 9( number of objects wanted)
=771.43

Answer 9

3x + 2y = 405
7x + 3y = 795

- 9x - 6y = - 1215
14x + 6y = 1590-------ADD

5x = 375
x = 75

225 + 2y = 405
2y = 180
y = 90

x = 75 , y = 90