Any geniuses here?

[.sarah]

I need help with my SAT prep class. I'm usually good with word problems but these have me stumped. Please just help me through them, I don't need the answers. This is an online class and I do not want to cheat!

Three years ago Bob was twice as old as Adam will be four years from now. Adam is "a" years old now. What is Bob's age in terms of Adam's age?
HELPFUL INFORMATION: Let a = Adam and b=Bob and let's write the equation as it is described b-3=2(a+4) then solve for b-Bob
a. 2a+6
b. 2a+11
c. a+4

If it takes p pounds of fertilizer to grow r rosebushes, how many pounds of fertilizer are needed for m rosebushes?
a. (rm)/p
b. r/(pm)
c. (pm)/r

Five books cost d dollars. How much money in cents will 7 books cost?
a. 7d
b. (100d)/5
c. (700d)/5

[Jessika]

1. Well you know that Adam's age (a) is TWICE the amount of Bob's age, plus eight. So if Adam is a years old, you will need to multiply it by two and add eight

2. noooo friggen clue. I know it has to do with ratios but without a number I can't get it LOL

3. If five books cost D dollars, then you would find it easier to find out how much EACH book cost, so you would need to divide d / 5. Then after you find that price, you can multiply it by seven.

I hope I helped without giving too much away... Because GOSH its been years since I've taken any math classes LOL

[.sarah]

I just did what you said and re-submitted and got the answers for all three wrong again Oh, and when I say this, I'm not mad at you LOL. I'm just frustrated.

SO, I'm going to edit the post with the remaining three answer choices and wait for more people to reply. I only have one more submission.

[Jessika]

Well I can tell you the answer to the first and last one and then maybe explain to you how I got it??

[.sarah]

Well I can tell you the answer to the first and last one and then maybe explain to you how I got it??

Okay

b-3=2(a+4) then solve for b

Distribute first, so:
b-3=2a+8

Get b alone by adding 3 to both sides:
b=2a+11

So for the first question b. is the answer. I'll try more if you are still stumped, I am eating dinner right now.

Ah, thanks! I didn't do the distributive and that was the problem.

[boscibo]

I edited out the answer I had posted, I didn't read you didn't want the answer!

[ILoveMyAbbyGirl]

The answer to the first one is b=2a+11. Simply just solve for b. They give you b-3=2(a+4). Add three to both sides to get b=2a+8+3. Add together and get b=2a+11.

The second one, you could set up as a ratio. p over r (it takes p pounds to plant r rosebushes) equals x over m (x number of pounds to get m number of rosebushes). So it should look like p/r = x/m . Cross multiply (p times m and r times x) and you will get pm = rx. Divide by r and get (pm)/r.

Third: Like Jess said, divide d by five, and you will get d/5. Then multiply by 100 to get the cents. You would get 100d/5. That is the price in cents for ONE BOOK. You need SEVEN. So you will multiply by 7, and get 700d/5.

[.sarah]

The answer to the first one is b=2a+11. Simply just solve for b. They give you b-3=2(a+4). Add three to both sides to get b=2a+8+3. Add together and get b=2a+11.

The second one, you could set up as a ratio. p over r (it takes p pounds to plant r rosebushes) equals x over m (x number of pounds to get m number of rosebushes). So it should look like p/r = x/m . Cross multiply (p times m and r times x) and you will get pm = rx. Divide by r and get (pm)/r.

Third: Like Jess said, divide d by five, and you will get d/5. Then multiply by 100 to get the cents. You would get 100d/5. That is the price in cents for ONE BOOK. You need SEVEN. So you will multiply by 7, and get 700d/5.

Ah, thanks!! That makes complete sense

I just submitted it and got them all right. Thank you again!!

EDIT: Thanks, Jess and boscibo for your help!

[boscibo]

b-3=2(a+4) then solve for b (I'm not a genius, but have had algebra recently)

Distribute first, so:
b-3=2a+8

Get b alone by adding 3 to both sides:
b=2a+11

I'll try more if you are still stumped, I am eating dinner right now.

[Van10]

Oh no, not math!
I have no idea what the answers would be, sorry.

[buckner]

Oh darn, everyone beat me to it! LOL, I wanted to show off my mad math skills.

Do you understand them now, Sarah? If not, let me know. I can explain them step by step in detail. Megan did a terrific job, just making sure you understand. It's easy to go "yes, I get it" WHILE the problem is being done, but when you have to do it yourself it can get a bit sticky.

I'm glad you got help!! Such smart people on PT.

Math is also my favourite subject, I kick total butt in it. Right now, I'm taking AP AB Calculus (Calculus 1 as a senior in highschool and I get college credit after I take my AP Calc test in May) and I LOOVVEEEE Algebra. There have been many cases in this class where it asks us to find something, and we (the nerds.. hehe) sit there, finding derivatives, integrals, and using several pieces of paper, and it could've been done with a simple equation. LOL But hey! We got to the right answer, we just found a lot of other stuff too! I often overlook the "easy" ways unless I'm aware of what technique I'll have to use. But for my AP test in May, I'm looking forward to whizzing right through it using all my short-cuts. Sometimes I remember to use them, but other times it's just good practice to go the long way!!