The answer is the first one 125
In the number 880, the first eight is ten times that of the
second eight. This is the first way in which the 8’s are related to one
another. The second way that the two 8’s are related is that is that if the
both 8’s change their respective places, then also the number will remain the
same. Since in this case the number in the tens place and the hundreds place
are same, so interchanging them will not have any effect on the overall number.
Number of ways to select 3 books from 13 books for adoption is 286 .
<u>Step-by-step explanation:</u>
A Permutation is an ordered Combination. When the order does matter it is a Permutation. There are basically two types of permutation:
- Repetition is Allowed: such as the lock above. It could be "333".
- No Repetition: for example the first three people in a running race. You can't be first and second.
Formula is given by:
, where n is the number of things to choose from, and we choose r of them, no repetitions, order matters. Here , n=13 , r=3.
⇒ 
⇒ 
⇒ 
⇒ 
⇒ 
∴ Number of ways to select 3 books from 13 books for adoption is 286 .
The equation is y=mx+c
C=8
M=-1