Math problems??

Question

1. Linda put $800 in a regular savings account and $1000 in a special account. In one year she earned $120 in interest. Her brother invested $1000 in the regular account. He earned $144 in interest. What are the interest rates on each type of savings account?

2. A tank can be filled by letting pipe A run for 3 hours and pipe B run for 2 hours, or by letting pipe A run for 2 hours and pipe B for 4 hours. How long does it take each pipe running alone to fill the tank?



Pls. answer it i need it right now pls. i'm begging you pls. pls. pls.

Answer 1

(1) Let R be the interest rate in the regular account and S be the interest rate in the special account.

800 * R + 1000 * S = 120
1000 * R = 144

Use the second equation to solve for R, then the first to solve for S.

(2) Let A and B be the flow rates for pipes A and B

3A + 2B = 2A + 4B

This simplifies to

A = 2B

Substitute this for A in the first equation and solve for B, then use the result and the second equation to solve for A.

Answer 2

1.. Assuming her brother only had the regular account, you didn't mention he had a special account.

800x+1000y=120
1000x=144 So, x=14.4% on the regular account
That means y=0.48% the rate on the special account.. What's so special about it?

2. 3x+2y=1 and 2x+4y=1....x=1/4 and y=1/8
So pipe A fills 1/4 the tank an hour, and pipe B 1/8 an hour.
Pipe A would therefore take 4 hours, pipe B would take 8 hours.

Answer 3

1)

We can calculate the interest of regular savings by using her brother's numbers:

1000 (1+x) = 1144
1000 + 1000x = 1144
1000x = 144
x = 144/1000 = .144 (or 14.4%)

Now, we can write her interest as:

800(.144) + 1000y = 120
115.2 + 1000y = 120
1000y = 4.8
y = 0.0048 = 0.48%


2)
If A and B are the pipe flow rates, then:

3A + 2B = 2A + 4B
A = 2B

3A + 2B = 1
3(2B) + 2B = 1
8B = 1
B = 1/8 (rate of B per hour) so B takes 8 hours to fill alone

Since A = 2B, A would take 4 hours alone.

Best of luck!

Answer 4

1.
144/x=1000/100 -> x=14,4 % regular account
14,4*800=115,2
120-115,2=4,8
4,8/x=1000/100 -> 0,48 % special account
2.
x=volume of water that the A pipe fills in an hour
y=..........................................B.................................
V=tank volume

3x+2y=V
2x+4y=V

multiplying by -2 the first ecuation and add to the sec one and you have
-6x+2x= -V -> 4x= V Pipe A needs 4 hours

multiplying the first one by -2 and the second one by 3 and adding them will make
8y=V Pipe B needs 8 hours

Answer 5

1)14.4 % in a normal account
0.48% in special account

2)A=4 hours
B=8 hours