zero
double - is actually plus
Answer:
Step-by-step explanation:
Rule Example
+(+) Two like signs become a positive sign 3+(+2) = 3 + 2 = 5
−(−) 6−(−3) = 6 + 3 = 9
+(−) Two unlike signs become a negative sign 7+(−2) = 7 − 2 = 5
−(+) 8−(+2) = 8 − 2 = 6
2x5.4x4.5x4.2x5.3x3. 5.5x3
For this case we have an equation of the form:
y = A * (b) ^ t
Where,
A: initial amount
b: decrease rate
t: time in years.
Substituting values we have:
7 = A * (0.5) ^ ((1/20) * t)
For t = 45 years we have:
7 = A * (0.5) ^ ((1/20) * 45)
Clearing A:
A = 7 / ((0.5) ^ ((1/20) * 45))
A = 33.3
Answer:
the density of the substance when it was deposited 45 years ago was:
A = 33.3 milligrams per square centimeter
