A10 pound block of lead-210 has a half-life of 22 years. what percentage of the block still contains lead-210 after 60 years?
1.5%
15%
77%
27%

The percentage of the block contains 15% after 60 years.

Explanation:

Step 1: Formula for half-life time

To calculate the half-life time we will use the following formula:

At = A0 * 1/2 ^(x/t)

With At = the quantity after a time t

A0 = The quantity at time t = 0 (start)

x = time in this case = 60 years

t= half-life time = 22 years

Step 2: Calculate the percentage after 60 years

In this case: after 60 years the percentage will be

A0= 10 * 1/2 ^(60/22)

A0 = 1.5

A0 / At  = 1.5 /10 = 0.15

0.15 *100% = 15 %

The percentage of the block contains 15% after 60 years.

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