Answer:
<u>The sum of their ages now is 13</u>
Step-by-step explanation:
Dally's age = x
Dilly's age = x - 7
In 4 years time Dilly will be half Dally’s age, therefore:
Dilly's age plus four equals to half of Dally’s age plus four,
replacing with the values and variables we know:
x - 7 + 4 = (x + 4) /2
x - 3 = (x + 4) /2
2x - 6 = x + 4 (Multiplying by 2 at both sides)
2x - x = 4 + 6 (Like terms)
x = 10 ⇒ x - 7 = 3
<u>The sum of their ages now is 13 (10 + 3)</u>
Answer:
212.9 years
Step-by-step explanation:
Given that the half-life of cesium-137 is 30 years. Suppose we have a 170 mg sample
P0 = 175
P(30) = 87.5
So we can write equation as

b) After 60 years t = 30
In 30 years it becomes half and hence in 60 years it would become 1/4
i.e.
mg
c) If P(t) =1, let us find t

212.9
Answer:
The total is 49.5
Step-by-step explanation:
15.8+17.42+16.28
Answer:
The required probability is 0.988.
Step-by-step explanation:
Consider the provided information.
Based on a poll, 67% of Internet users are more careful about personal information when using a public Wi-Fi hotspot.
That means the probability of more careful is 0.67
The probability of not careful is: 1-0.67 = 0.33
We have selected four random Internet users. we need to find the probability that at least one is more careful about personal information.
P(At least one careful) = 1 - P(None of them careful)
P(At least one careful) = 1 - (0.33×0.33×0.33×0.33)
P(At least one careful) = 1 - 0.012
P(At least one careful) = 0.988
Hence, the required probability is 0.988.
The result may be higher because of the convenience bias in retrieving the sample. Because the survey subjects volunteered to respond not random.