Samuel needs to estimate the product of 24 x 395.
First method
We round the number to nearest tens
24 can be rounded to 20 because we have 4 on ones place
395 can be rounded to 400 because we have 5 in ones place so we add 1 with 9 and it becomes 10 . so we add 1 with 3 and got 400
20 * 400 = 8000
Second method:
We round the number to nearest hundreds place
24 have no number in hundreds place so it remains 24
395 can be rounded to 400 because we have 9 in tens place.
24 * 400 = 9600
The radius is 4.
Find the radius of the circle whose equation is (x + 5)2 + (y + 8)2 = 16

2) 5.625 mg will be left
Explanation:
1) Half-life = 17.5 days
initial amount of Arsenic-74 = 90 mg
To get the equation, we will use the equation of half-life:


2) we need to find the remaining amount of Arsenic-74 after 70 days
t = 70

So after 70 days, 5.625 mg will be left
He ran 14 km, multiply 6 by 2 and 1/3.
$27
2.65 x 2 (since he has to go both to and from work each day) = $5.30
Add the daily cost of the water bottle (1.45) to make his total cost for one day, which is 6.75
Multiply this number by 4 (because he goes 4 days a week) to get $27 for one week.