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December 20, 2014

December 20, 2014

Posted by **Tamir** on Friday, June 11, 2010 at 10:19pm.

1. One-third of a number is 5 less than half of the same number. What is the number?

My answer:

1/3x = 1/2x - 5

6(1/3x) = 6(1/2x) - 6( 5)

2x =3x - 30

2x - 2x = 3x - 30 - 2x

0 = x - 30

0 + 30 = x - 30 + 30

30 = x

x = 30

And to check:

1/3x = 1/2x - 5

1/3(30) = 1/2(30) - 5

30 / 3 = 30 / 2 - 5

10 = 15 - 5

10 = 10

2. The sum of a number and its reciprocal is 10/3. What is the number?

My Ans:

x+1/x= 10/3

(x^2+1)/x= 10/3

3 ( x^2+1)= 10 x

3x^2+3= 10x

3x^2-10x+3= 0

( 3x-1) ( x-3) = 0

3x-1= 0

x= 1/3

x-3= 0

x= 3

Check:

x+1/x= 10/3

3 + 1/3= 10/3

(9+1)/3= 10/3

10/3= 10/3

3. An investment of $1500 paid interest of $45 during a certain period. How much interest would an investment of $2000 invested at the same rate for the same length of time pay?

My Ans:

45/1,500=X/2,000

1,500X=45*2,000

1,500X=90,000

X=90,000/1,500

X=$60

Check:

45/1,500=60/2,000

90,000=90,000

4. In baseball a player's batting average is the ratio of hits to the number of times he or she has batted. Thus, if the player has an average of .3000, it means he or she got 300 hits in 1000 at bats. In order to have an average of .300, how many hits would the batter have to get in 400 times at bat?

My Ans:

batting average=(hits)/(times batted)

your batting average =.300

times batted=400

hits=x

.300 = x/400

(400).(.300)= 400x/400

120 = x

Check:

.300 = 120/400

.300 = 300

Thanks in advance everyone.

- Algebra -
**Jen**, Friday, June 11, 2010 at 11:17pm1, 2, and 4 are right. I'm not sure about 3.

- Algebra -
**Reiny**, Friday, June 11, 2010 at 11:49pm#3 is correct

another way to do #3 is to simply set up a ratio

x/2000 = 45/1500

x = 45(2000)/1500

= 60

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