3/8=0.375
2/5=0.4
0.38=0.38
0.375<0.38<0.4
therefore: 3/8,0.38,2/5
*Remember that you can convert fractions to decimals by dividing the numerator by the denominator! This makes it much easier to compare :)
Assuming simple interest (i.e. no compounding within first year), then
At 6%, interest = 10000*0.06=$600
At 9% interest = 10000*0.09 = $900
Two ways to find the ratio
method A. let x=proportion at 6%
then
600x+900(1-x)=684
Expand and solve
300x=900-684=216
x=216/300=0.72 or 72%
So 10000*0.72=7200 were invested at 6%
10000-7200=2800 were invested at 9%
method B: by proportions
Ratio of investments at 6% and 9%
= 900-684 : 684-600
=216 : 84
= 18 : 7
Amount invested at 6% = 18/(18+7) * 10000 = 0.72*10000 = 7200
Amount invested at 8% = 7/(18+7)*10000=0.28*10000=2800
The variable in this equation is b, therefore we have to calculate the value of b.
-38=2b+25-(-7b)
-38=2b+25+7b
2b+7b=-38-25
9b=-63
b=-63/9
b=-7
Answer: the value of the variable is b=-7
We can check it out this answer:
-38=2b+25-(-7b)
-38=2(-7)+25-(-7(-7))
-38=-14+25-49
-38=-38
we know that
step 1
multiply 
by 
so
step 2
Divide numerator and denominator by 
therefore
the answer is
To solve this problem you have to set up a proportion. To form one side of the proportion you use "is over of" meaning what number represented by is, in this case 18, is placed over the number represented by of, 3000.
Since you are finding the percent of something, youre x value is placed above "100" because percent values are most commonly out of 100%.
So now your proportion will look like
To solve the proportion you cross multiply and divide. So you multiply 100 and 18 since they are crossed from each other, then divide 1800 by 3000. The answer is .6. 18 is .6% of 3000.
