Question 1199890
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The simple interest formula is
i = P*r*t
where,
i = interest
P = deposit
r = interest rate in decimal form
t = number of years


Let 
x = amount deposited at 3% rate
7000-x = amount deposited at 7% rate
The two items add to $7000


For the 3% account
i = P*r*t
i = x*0.03*1
i = 0.03x


For the 7% account
i = P*r*t
i = (7000-x)*0.07*1
i = 490-0.07x


Total interest = 0.03x+(490-0.07x)
Total interest = -0.04x+490


Set that equal to $250 and solve for x.
Total interest = 250
-0.04x+490 = 250
-0.04x = 250-490
-0.04x = -240
x = -240/(-0.04)
x = 6000
$6000 was invested at 3% interest rate.


Then use mental math to determine the remaining amount invested must be $1000


Or you can say: 7000-x = 7000-6000 = 1000


Check:
6000+1000 = 7000
6000*0.03+1000*0.07 = 250
Both conditions are verified.



Answer:
<font color=red>$6000</font> invested at 3%
<font color=red>$1000</font> invested at 7%
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