Physics problem about springs PLEASE HELP

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A 2 kg block hangs from a spring. A 253g body hung below the block stretches it a further 2.5cm. What's the spring constant? Use g=9.8N/kg. Calculate the value to 1 decimal place and use N/m as your unit.

AND
A 1.8kg block hangs from a spring. A 221g body hung below the block stretches it a further 3.8cm. If the 221g body is removed and the block set into oscillation, what is the period of the motion? Use g=9.8N/kg. Calculate the value to 2 decimal place and use second as your unit.
 
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In order to get help, you should post an attempted solution.

Here is a hint: Write the force balance equation for a) just the first block and b) both blocks together. How can you then use these two equations to obtain an expression for k in terms of the known values?

for the second part, if I were to do it, I would set up a force balance equation (left side in terms of displacement x from the rest postion, right side in terms of acceleration = d^2x/dt^2) with initial conditons dx/dt(0)=0 and x(0)=-x1. This could then be solved, and the period of the solution can be obtained.
 
What a know/think!

number 1??
I THINK.. it is
we know F=KX & W=MG
since F=W, KX=MG
so K*d=2kg*G also K*(d+2.5cm)=2.253kg*G
so K=(2kg*G)/d also K=(2.253kg*G)/(d+2.5cm)
then (2kg*G)/d = (2.253kg*G)/(d+2.5cm)
we solve for d: (d+2.5cm)/d= (2.253kg*G)/(2kg*G)
G cancels out: (d+2.5cm)/d= 2.253kg/2kg
so 1+(2.5cm/d)= 2.253/2
2.5cm/d= 2.253/2-1
d= 2.5cm/(2.253/2-1)=
now that you have d and d+2.5cm
you can plug into equation F=KX or K=F/X which is K=MG/X
use K=MG/X
K=2kgG/d you know G and d so you have K which is spring constant.
K=99.2N/m

Number 2..
NOT A CLUE..
PLEASE HELP
 
To solve this, I first used the units to work out that a= m* a/m, i.e. t=z/λ. This would allow you to determine the time duration within an interval section by section and then add this to the previous ones to obtain the age of the respective layer. However, this would require a constant thickness per year for each interval. However, since this is most likely not the case, my next consideration was that the age must be the integral of a 1/λ(z) function, which I cannot model.
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