Alan

You have found two of the possibilities EP.

Volume of cylinder = pi*r²*h

V2 = pi*r2²*h2

V1 = pi*r1²*h1

V2/V1 = (r2/r1)²*(h2/h1)

r2/r1 = 0.9, h2/h1 = 1.1, so V2/V1 = 0.9²*1.1

Hence V2 = 0.9²*1.1*100 ft³

We can immediately multiply the first equation by 5, so we have the two equations:

15x + 5y = 5a

2x + 5y = 2a

Subtract the second from the first:

13x = 3a

Rearrange and divide by 3:

a = (13/3)*x

Substiute 2 for x:

a = (13/3)*2  or a = 26/3

(tertre added when he/she should have subtracted).

The diagonals of a parallelogram bisect each other. This means:

y = 2x + 1

5y = 7x + 11

You have two equations in two unknowns.

Can you take it from here?

Percentage increase is given by [(2nd order/1st order) - 1]*100

More generally, if you want the equation of the line in the form y = mx + c, then m = -2/3 and you find c from: 1 = -(2/3)*2 + c   (so c = 7/3).

If the two ponts are (1, 3) and (2, 3) then the line between them is horizontal (the two y-values are the same), so it has zero slope.

In general with points (x1, y1) and (x2, y2) the slope is given by (y2 - y1)/(x2 - x1)

The question stipulates non-negative numbers, so only one of Rom's sets is valid.  If the question required integer solutions then (0,0,0, 2) is also a solution.  However, it specifies real numbers (not necessarily integers), so there may well be other solutions, but so far I haven't put any thought into what those might be!

The only other one I can think of is (0, 0, √2, √2).

As follows:

You’re right.  The explanation was even more confusing than I first thought!