One boat travelling 15 mph goes 47 miles downstream in the same amount of time that another boat going 20 mph goes 40 miles upstream. how fast is the current in mph? (round your answer to the nearest tenth of miles per hour and enter only the numerical part

  3.9 mi/h

Step-by-step explanation:

We assume that the given speeds are the speeds of the boats relative to the water. If c is the speed of the current, we have ...

  time = distance/speed

  47/(15 +c) = 40/(20 -c)

  47(20 -c) = 40(15 +c) . . . . . . multiply by (20-c)(15+c)

  940 -600 = 40c +47c . . . . . add 47c-600

  340 = 87c . . . . . . . . . . . . . . . simplify; next divide by 87

  c = 340/87 ≈ 3.9080 . . . . mi/h

The speed of the current is about 3.9 mi/h.

d

step-by-step explanation:

hello and welcome!

so, when we see the words "proportional" along with a table, we need to know that we're looking numbers that divide by the same thing.

looking at this table, we simply have to do a trial and error, and divide to see which numbers have the same quotient. if you look at choice a & c, they both have equal quotients for three of the numbers, with one exception, so those can't be the answer. looking at b, there is no similarity, so that can't be it. then, we see d; if you divide all the numbers in the table, you'll see that they all divide by two, which is a proportional relationship, and our answer!

also, always remember that the x will always be the number that goes into y, and somewhere behind this table, is a formula. for this specific table, the formula would be:

since our x-value is being divided by two to get the y-value. and if they were to ask for more numbers in the series, this is the formula you would use to find them.