A motorboat takes 3 hours to travel 108 km going upstream. The return trip takes 2 hours going downstream. What is the rate of t
1 answer:
Recall your d = rt, distance = rate * time.
let's say the boat has a still water rate of "b", and the current has a a rate of "c", ok.... when the boat is going upstream, is not really going "b" fast, is going slower at "b - c", due to the current going in the opposite direction.
when the boat is coming downstream, is not going "b" fast either, is going faster, is going "b + c", due to the current adding speed to it.
we know the trip up was 108 kms, thus the return trip is also 108 kms.
and surely you know how much that is.
what's the boat's speed? well, 36 + c = b.
let's say the boat has a still water rate of "b", and the current has a a rate of "c", ok.... when the boat is going upstream, is not really going "b" fast, is going slower at "b - c", due to the current going in the opposite direction.
when the boat is coming downstream, is not going "b" fast either, is going faster, is going "b + c", due to the current adding speed to it.
we know the trip up was 108 kms, thus the return trip is also 108 kms.
and surely you know how much that is.
what's the boat's speed? well, 36 + c = b.
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#2. First, we factor each polynomial. Then, if any terms on both the top and the bottom of the fraction match, they cancel out. So... we do just that. You end up with:
Notice there's an (x-4) on both top and bottom. So they cancel out. That leaves us with your answer of
#3. We do the same thing as above then multiply and simplify. In the interest of space, I'll cut straight to some simplification.
Now we start cancelling. For the first fraction, there are 3 (x+2)'s on top and 1 on the bottom so we will cancel out the one on the bottom and leave 2 (x+2)'s on top. There are no more polynomials to cancel out so now we multiply across:
10 and 6 share a GCF of 2 so we divide both of those by 2. This leaves us with the final answer of:
#4. This equation introduces division and because of it, we must flip the second fraction to make the division sign into a multiplication symbol. Again for space, I'll flip the fraction and simplify in one step.
Now we do our cancelling. First fraction has (x - 2) in the top and bottom. They're gone. The first fraction has a (x + 4) on the bottom and the second fraction has one on the top. Those will also cancel. This leaves you with:
3 and 6 share a GCF of 3 so we divide both numbers by this. This leaves you with your final answer:
#5. We are adding so we first factor both fractions and see what we need to multiply by to make the denominators the same. I'll do the former first. (10 - x) and (x - 10) are not the same so we multiply the first equation (top and bottom) by (x - 10) and the second equation by (10 - x). Because they will now have the same denominator we can combine them already. This gives us:
Now we FOIL each to expand and then simplify by combining like terms. Again for space, I'm just showing the result of this; you end up with:
Now we factor the top. This gives you 2 (x - 10)'s on top and one on bottom. So we just leave one on the top and cancel the bottom one out. This leaves you with your answer:
#6. Same process for this one so I won't repeat. I'll just show the work.
becomes
which equals
giving you the final answer
#7. For this question we find the least common denominator to make the denominators match. For 5, x, and 2x, the LCD is 10x. So we multiply top and bottom of each fraction by what would make the bottom equal 10x. This rewrites the fraction as:
Simplify to get:
After simplifying again, you end up with your final answer:
Notice there's an (x-4) on both top and bottom. So they cancel out. That leaves us with your answer of
#3. We do the same thing as above then multiply and simplify. In the interest of space, I'll cut straight to some simplification.
Now we start cancelling. For the first fraction, there are 3 (x+2)'s on top and 1 on the bottom so we will cancel out the one on the bottom and leave 2 (x+2)'s on top. There are no more polynomials to cancel out so now we multiply across:
10 and 6 share a GCF of 2 so we divide both of those by 2. This leaves us with the final answer of:
#4. This equation introduces division and because of it, we must flip the second fraction to make the division sign into a multiplication symbol. Again for space, I'll flip the fraction and simplify in one step.
Now we do our cancelling. First fraction has (x - 2) in the top and bottom. They're gone. The first fraction has a (x + 4) on the bottom and the second fraction has one on the top. Those will also cancel. This leaves you with:
3 and 6 share a GCF of 3 so we divide both numbers by this. This leaves you with your final answer:
#5. We are adding so we first factor both fractions and see what we need to multiply by to make the denominators the same. I'll do the former first. (10 - x) and (x - 10) are not the same so we multiply the first equation (top and bottom) by (x - 10) and the second equation by (10 - x). Because they will now have the same denominator we can combine them already. This gives us:
Now we FOIL each to expand and then simplify by combining like terms. Again for space, I'm just showing the result of this; you end up with:
Now we factor the top. This gives you 2 (x - 10)'s on top and one on bottom. So we just leave one on the top and cancel the bottom one out. This leaves you with your answer:
#6. Same process for this one so I won't repeat. I'll just show the work.
#7. For this question we find the least common denominator to make the denominators match. For 5, x, and 2x, the LCD is 10x. So we multiply top and bottom of each fraction by what would make the bottom equal 10x. This rewrites the fraction as:
Simplify to get:
After simplifying again, you end up with your final answer: