Answer:
Step-by-step explanation:
For a first order decay, fraction remaining = 0.5n where n = number of half lives elapsed.
fraction remaining = 55% = 0.55
0.55 = 0.5n
log 0.55 = n log 0.5
-0.2596 = -0.301 n
n = 0.8625 = # of half lives elapsed
0.8625 half lives x 2.5 billion years/half live = 2.16 billion years have elapsed = age of the rock
b) 0.15 = 0.5n
log 0.15 = n log 0.5
-0.824 = -0.301 n
n = 2.74 half lives
2.5 billion years/half life x 2.74 half lives = 6.85 billion years = age of rock
Answer:
x = 1 , y = 2
Step-by-step explanation:
Solve for substitution
25 is equal to 20% of 125
As the increase is 75 (200-125), you've then got to divide the increase by each part to find out how many times it increases.
75/25= 3
20*3= 60
Therefore, there is an increase of 60%
Hope this helps :)