Answer :
Let the number of days they take to consume same amount be d.
Celia's equation for consumption is :
Y = 1200 + 100d
Ryan's consumption equation is :
Y = 3230 - 190d
We are looking for a time when these two will be equal.
We therefore equate the two equations as follows :
3230 - 190d = 1200 + 100d
We want to get the value of d.
3230 - 1200 = 100d + 190d
2030 = 290d
d = 2030/290
d = 7
The answer is thus :
7 days.
Celia's equation for consumption is :
Y = 1200 + 100d
Ryan's consumption equation is :
Y = 3230 - 190d
We are looking for a time when these two will be equal.
We therefore equate the two equations as follows :
3230 - 190d = 1200 + 100d
We want to get the value of d.
3230 - 1200 = 100d + 190d
2030 = 290d
d = 2030/290
d = 7
The answer is thus :
7 days.