Answer:
7
Step-by-step explanation:
Concept to Know: "A number is a perfect square if and only if it has odd number of positive divisors
"
Find all the squared values that lies between 360 and 630
360< 19², 20², 21², 22², 23², 24², 25² < 630
19², 20², 21², 22², 23², 24², and 25² are all the squared values that lies between 360 and 630. There are seven of those squared numbers so the answer is 7.
For the equation 
take the 
from both sides:
Find x:
Answer: correct choice is D
Answer:
B. 4x ≤ 320
Step-by-step explanation:
Not sure how to explain my thinking. However, 4x must be smaller than 320 because she cannot spend more than that.
Answer: 145.5
Step-by-step explanation:
A) On the first place we can put 9 digits, on the second 9, on the third place 8 and on the last place 7 ( because no digits can be repeated ):
9 · 9 · 8 · 7 =4536 numbers
b) There are 5 odd digits can be repeated. So:
5 · 10 · 10 · 5 = 2500 numbers
c) On the first place we can put:5,6,7,8,9 (5 digits) On the last place is just one (0), because the number must be divisible by 10:
5 · 10 · 10 · 1 = 500 numbers
d) on the first place we can put 2 digits ( 1, or 2 - there are no 4-digit numbers starting with 0). The last digit must be even, but the order can be:
X - odd - odd - even 2 · 5 · 4 · 5 = 200
X - odd - even - even 2 · 5 · 5 · 4 = 200
X - even - odd - even 2 · 5 · 5 · 4 = 200
X - even - even - even 2 · 5 · 4 · 3 = 120
Finally: 200+ 200 + 200 + 120 = 720 numbers
