$\text{Let the number of dimes be x, then as per the friend the number of }\\
\text{quarters should be 8 more than dimes, so number of quarters}=x+8\\
\\
\text{we know that the value of 1 dime is }\$ 0.10 \text{ value of one quarter is }\$0.25\\
\\
\text{And since the total value of quarters and dimes is }\$2.80, \text{ so we have}\\
\\
0.10(x)+0.25(x+8)=2.80\\
\\
\Rightarrow 0.10x+0.25x+2=2.80\\
\\
\Rightarrow 0.35x=2.80-2\\
\\
\Rightarrow 0.35x=0.80$

$\Rightarrow x=\frac{0.80}{0.35}=2.29\\
\\
\text{so if we take 2 dimes then we'll have to take 10 quarters according to friend.}\\
\\
\text{So the statement of friend is }$ WRONG

6 0

2 years ago

The half-life of a certain substance is 20 years. How much of a 100 gram sample will be left after 20 years?

cluponka [151]

$\bf \textit{Amount for Exponential Decay using Half-Life} \\\\ A=P\left( \frac{1}{2} \right)^{\frac{t}{h}}\qquad \begin{cases} A=\textit{accumulated amount}\\ P=\textit{initial amount}\dotfill &100\\ t=\textit{elapsed time}\dotfill &20\\ h=\textit{half-life}\dotfill &20 \end{cases} \\\\\\ A=100\left( \frac{1}{2} \right)^{\frac{20}{20}}\implies A=100\left( \frac{1}{2} \right)^1\implies A=50$