He messed up step 2 he added instead of multiplying
We divide both sides by 7 which makes n alone. Which is n=m/7.
a) 9 toilet rolls cost $ 4.23
1 toilet roll costs $ x
9x = 4.23 * 1
x= 4.23 / 9
x = 0.47
So in first case one toilet roll costs $ 0.47.
b) 4 toilet rolls cost $1.96
1 toilet roll costs $ x
4x = 1.96 * 1
x = 1.96 / 4
x = 0.49
So in second case one toilet roll costs $ 0.49.
0.47 < 0.49
The toilet roll in first case is cheaper than the toilet roll in second case.
Hope this heps!
A cross section is the shape we get when cutting straight through an object. The cross section of this object is a triangle. It is like a view into the inside of something made by cutting through it.
