commercial math help..plz
given that carbon decays at a constant rate in a such a way that it reduces to 20% in 1562 years. the age of the wooden piece in which the carbon is only 4% of the original
given that carbon-14 decays at a constant rate in such a way that it reduced to 25% in 1244 years.. find the age of the tree in which the carbon is only 6.25% of the original
the simple interest and compound interest on a certain sum for 2 years are rs. 800 and rs. 880 respectively. the rate of interest (in % p.a.) on both the sums is the same. if the interest on the sum lent at compound interest is compounded annually, find the rate of interest (in % p.a.)
A man wants to divide rs.145000 between his son and daughter who are 12 years and 14 years respectively, in such a way that the sum invested at the rate of 25/3% per annum compounded annually will give the same amount to each, when they attain 16 years. how should he divide the sum
A man invested one-fifth of the capital at 5% p.a., one - sixth of the capital at 6% p.a., and the rest at 10% p.a., simple interest. If the annual interest received on his investment is rs.150, then find the capital.
How much % greater than the cost price should a shopkeeper mark his goods so that after allowing a discount of 22% on the marked price, he gains 17%.
thanks a lot.(Bow)(Bow)
Re: commercial math help..plz
Let 100 be the cost price and 100 + x be the market price. The selling price is (100 + x)0.78 . The profit will be (100+x)0.78 - 100 = 117. Solve for x.
Re: commercial math help..plz
For the first two, we may use exponential decay:
=A_0e^{-kt})
where 
We are being asked in these problems to find an age, which means we should solve for 
:
}{A_0}=e^{-kt})
}{A_0} \right))
} \right))
Now, suppose we know:
=a \cdotA_0)
where 
.
Hence, we may state:
)
}{t_1})
and so:
}\cdot\ln\left(\frac{A(t)}{A_0} \right))
In both problems, we may take 
hence:
}\cdot\ln(A(t)))
Now, can you identify the parameters for the two problems?
