Answer:
15) 300%
Explanation:
15)
Let the item originally cost n dollars.
The new incorrect price is (n-.6n).
So we want to find k such that (n-.6n)+k(n-.6n)=n+.6n
since we actually wanted it to be (n+.6n).
So we have (n-.6n)+k(n-.6n)=n+.6n
Distribute:
n-.6n+kn-.6nk=n+.6n
Subtract n on both sides
-.6n+kn-.6nk=.6n
We are trying to solve for k. So add .6n on both sides:
kn-.6nk=1.2n
Divide both sides by n:
k-.6k=1.2
.4k=1.2
Divide both sides by .4
k=1.2/.4
k=3
So 3=300%.
The incorrect price must be increased by 300% to get to the proper new price.
Here is an example:
Something cost $600.
It was reduce by 60% which means it cost 600-.6(600)=600-360=240
This was the wrong price.
We needed it to be increased by 60% which would have been 600+360=960.
So we need to figure out what to increase I wrong price 240 to to get to our right price of 960.
240+k(240)=960
1+k=960/240
1+k=4
k=3
So 240*300%+240 would give me my 960.
16) Speed=distance/time
In the first half hour, she traveled 5 miles (8:30 to 9).
In 1/3 hour she traveled (5-2)=3 miles (9 to 9:20).
We are told not to do anything where she stayed still.
In the last half hour, she traveled (2-0)=2 miles (9:30 to 10).
The average speed=
.