A rectangular class seats 72 students. If the seats were arranged with 3 more seats in each row, the class would have 2 fewer rows. Find the original number of seats in each row.
How many liters of water must be added to 20 L of a 24% salt solution to make an 8% salt solution?
Two planes leave simultaneously from the same airport, one flying due north and the other flying due east. The northbound plane is flying 50 mi/hr faster than the eastbound plane. After 3 hours, the planes are 2440 miles apart. Find the speed of each plane.
Before you yell at me to do my own homework, keep in mind that I already did attempted these problems. These are the only three problems I keep missing on my math homework. Any help would be appreciated. There is no need to give me the answers, but it'll be helpful if you point me in the right direction.
2007-10-20 13:29:01 · 3 answers · asked by xılǝɥ ⋆ 5 in Science & Mathematics ➔ Mathematics
1) r=rows, s=seats.
r*s=72=(r-2)*(s+3)
r=72/s so substitute that for r in the above equation (((72/s-2)*(s+3)=72) and solve.
2) 24% of 20 liters = total amount of salt., x + amount of water to be added.
24% of 20 = 8% of (20+x) and solve for x.
3) n=northbound speed, e=eastbound speed, n also =e+50
Pythagorean Theorem problem:
Northbound distance=3n=3(e+50)
Eastbound distance=3e
(3(e+50))^2+(3e)^2=2440^2 and solve for e then add 50 for n.
2007-10-20 13:48:56 · answer #1 · answered by Tom 6 · 1⤊ 0⤋
x = original no of seats per row
Thus there are 72/x rows
If there were x+3 seats per row, there would be
72/(x+3) rows
where 72/(x+3) = 72/x - 2
72x = 72*(x+3) - 2x*(x+3)
2x^2 + 6x - 3*72 = 0
solve and get x = 9
This problem would have been a lot easier if you had just listed the factors of 72 and observed which ones work.
2007-10-20 14:27:31 · answer #2 · answered by Dr D 7 · 2⤊ 0⤋
i seriously have no idea.
2007-10-20 13:31:46 · answer #3 · answered by abc 2 · 0⤊ 1⤋