From the graph, the national debt in 1960 was 46%.
It was given that the national debt in 1960 is $0.3 trillion.
Let the GDP be represented by G. This means that 46% of this value is:
[tex]\Rightarrow\frac{46}{100}\times G[/tex]Equating this to the debt amount, we have:
[tex]0.3=\frac{46}{100}\times G[/tex]Solving for G, we have:
[tex]\begin{gathered} 46G=0.3\times100 \\ 46G=30 \\ G=\frac{30}{46} \\ G=0.65 \end{gathered}[/tex]Therefore, the GDP in 1960 was $0.65 trillion.