Question

Grandma bakes the world's best and favorite cookies. If grandma's cookies have a half life of 2 hours and she bakes 3 dozen cookies, how many hours will pass until only two cookies remain?

a. 56 minutes
b. 1 hour and 17 minutes
c. 1 hour and 10 minutes
d. 8 hours and 20 minutes

Answer 1

The time that pass until only two cookies left is 1.89 hour

Explanation:

Given as :

The number of cookies bakes in 2 hours = 3 dozen

∵ 1 dozen = 12 piece

So, In 3 dozen = 12 × 3 = 36 cookies

The Time required to bake 36 cookies = 2 hours

Now, Let The time required to bake 2 cookies = x hour

So, According to question

∵ The time required to bake 36 cookies = 2 hours

So, the time required to bake 1 cookies =
`(2)/(36)` =
`(1)/(18)` hour

∴The time required to bake 34 cookies =
`(1)/(18)` × 34

I.e The time required to bake 34 cookies =
`(34)/(18)` hour = 1.89 hour

Or, the time taken is 1.89 hours

Hence The time that pass until only two cookies left is 1.89 hour Answer