Can someone please help me

Determine the average speed of the current in a river if a boat moves at 20 miles/hour in still water and takes 3 hours to trave

Taya2010 [7]

The speed of the current in a river is 6 miles per hour

Solution:

Given that,

Speed of boat in still water = 20 miles per hour

Time taken = 3 hours

Distance downstream = 78 miles

To find: Speed of current

If the speed of a boat in still water is u km/hr and the speed of the stream is v km/hr, then:

Speed downstream = (u + v) km/hr

Speed upstream = (u - v) km/hr

Therefore, speed downstream is given as:

$\text{ speed downstream } = \frac{distance}{time} = \frac{78}{3}\\\\\text{ speed downstream } = 26 \text{ miles per hour }$

We know that,

Speed downstream = (u + v)

26 = 20 + v

v = 26 - 20

v = 6 miles per hour

Thus speed of the current in a river is 6 miles per hour

3 0

3 years ago

The amount c in grams of a 100 gram sample of carbon-14 remaining after t years is represented by the equation c= 100 (0.99988)t

tigry1 [53]

Answer: The amount of carbon-14 remaining after 4 years is 99.95 grams.

Step-by-step explanation:

Hi, to answer this question we simply have to substitute t=4 in the equation given and solve for c.

c= 100 (0.99988)^t

c =100 (0.99988)^4

c = 100 x 0.999520086

c= 99.95200864 ≅99.95 grams (rounded)

The amount of carbon-14 remaining after 4 years is 99.95 grams.

Feel free to ask for more if needed or if you did not understand something.

8 0

3 years ago

What is the constant proportionality of 3 cans and 9 balls

Masja [62]

The constant proportionality is whats left over

3 0

3 years ago

The total sales of a company (in millions of dollars) t months from now are given by S(t) = 0.03t3 + 0.5t2 + 9t + 4. Find S'(t).

o-na [289]

Answer:

S'(t) = 0.09t^2 + t + 9

S(2) = 24.24

S'(2) = 11.36

S(11) = 203.43 means that the sales of the company 11 months from now is $203,430,000.

S'(11) = 30.89 means that, 11 months from now, the rate at which sales change is $30,890,000 per month

Step-by-step explanation:

The derivate of the sales function S'(t) , which is the rate at which sales vary with time in months, is:

$\frac{dS(t)}{dt} =S'(t) = 0.09t^2 + t + 9$

S(2) is found by applying t=2 to S(t):

$S(2) = 0.03*(2^3) + 0.5*(2^2) + 9*2 + 4\\S(2)= 24.24$

S'(2) is found by applying t=2 to S'(t):

$S'(2) = 0.09*(2^2) + 2 + 9\\S'(2) = 11.36$

Since the sales function gives the amount of sales in millions of dollars,

S(11) = 203.43 means that the sales of the company 11 months from now is $203,430,000.

S'(t) represents the rate of change in sales in millions of dollars per month.

S'(11) = 30.89 means that, 11 months from now, the rate at which sales change is $30,890,000 per month

8 0

3 years ago

Melissa estimated the length of a room is her house to be 13 ft . The actual length of the room is 11 ft. Find the absolute erro

Trava [24]

Answer:

Step-by-step explanation:

4 cm

7 0

3 years ago