Answer:
Jenna had 25 quarters and 15 dimes.
Step-by-step explanation:
Let Q = the number of quarters and D = the number of dimes.
Then:
1) Q+D = 40 "One week she had 40 coins, all of them dimes and quarters...."
2) 0.25Q+0.1D = $7.75 "...she had a total of $7.75."
Rewrite equation 1) as: D = 40-Q and substitute into equation 2).
2a) 0.25Q+0.1(40-Q) = 7.75 Simplify the left side.
2b) 0.25Q+4-0.1Q = $7.75 Subtract 4 from both sides.
2c) 0.25Q-0.1Q = 3.75 Combine the like-terms on the left side.
2d) 0.15Q = 7.75 Divide both sides by 0.15
2e) Q = 25 and:
D = 40-Q
D = 40-25
D = 15
Jenna had 25 quarters and 15 dimes.
Answer:
The area of the rectangle is increasing at a rate of 84 square centimeters per second.
Step-by-step explanation:
The area for a rectangle is given by the formula:
Where <em>w</em> is the width and <em>l</em> is the length.
We are given that the length of the rectangle is increasing at a rate of 6 cm/s and that the width is increasing at a rate of 5 cm/s. In other words, dl/dt = 6 and dw/dt = 5.
First, differentiate the equation with respect to <em>t</em>, where <em>w</em> and <em>l</em> are both functions of <em>t: </em>
By the Product Rule:
Since we know that dl/dt = 6 and that dw/dt = 5:
We want to find the rate at which the area is increasing when the length is 12 cm and the width is 4 cm. Substitute:
The area of the rectangle is increasing at a rate of 84 square centimeters per second.
Answer:
.009 miles/hour
Step-by-step explanation:
This is the method you should take with unit conversions in general, just set up fractions so the units cancel out, like the 7.5 feet cancels out with the feet in the 1/5280 so miles is left on top.
Answer: i need more information 8 apples cost $4, 4???????
Step-by-step explanation:
Start by putting two coins on each side of the scale. If one side is higher, then the light coin must be in that pair (use a second weighing to determine which of that pair is the lightest.)
If the initial weighing shows the two pairs to be even, discard those four and go to the three others. Put two of the coins on the scale - one on each side. If one side stays higher, that coin is your light one. If however they are equal, the final unweighed coin must be the lighter coin.