Answer:
90% of the questions she answered correctly
Step-by-step explanation:
%age = 81/90 * 100= 90 % correctness
The stereo system costs $256.
Step-by-step explanation:
Given:
Cost of the stereo system = $320.
The discount Zenaida received = 20%.
To Find:
Cost of the stereo system after the discount=?
Solution:
Step1: Finding the discount amount:
Discount percentage =20
Discount amount = original cost × discount percent
Substituting the values,





Step 2: Removing the discounted amount from the original price
Final cost of the stereo system =original cost of the stereo system –discount amount
Substituting the values we get,
Final cost=320-64
Final cost=256
Result:
Thus the cost of the stereo system after discount is $256
Answer:
The mass of the pipe is 
Step-by-step explanation:
step 1
Find the volume of the steel pipe
The volume is equal to the area of outside circle minus the area of inside circle, multiplied by the length of the pipe
so
![V=\pi [r2^{2}-r1^{2}]L](https://tex.z-dn.net/?f=V%3D%5Cpi%20%5Br2%5E%7B2%7D-r1%5E%7B2%7D%5DL)
we have
---> the radius is half the diameter
---> the radius is half the diameter


substitute
=59.66\ cm^{3}](https://tex.z-dn.net/?f=V%3D%283.14%29%5B1%5E%7B2%7D-0.9%5E%7B2%7D%5D%28100%29%3D59.66%5C%20cm%5E%7B3%7D)
step 2
Find the mass
The mass is equal to the density multiplied by the volume
so

There are 10³×26³ = 17,576,000 possible different plates. If any of those is randomly chosen, the probability of picking one in particular is
... 1/17576000 ≈ 0.0000000569