Question

which of these equations is correct check all that apply

Answer 1

Scientific notation

We know that the power of 10 indicates the number of zeros after 1 the number has:

$\begin{gathered} 10^6=1,000,000 \\ 10^7=10,000,000 \\ 10^8=100,000,000 \end{gathered}$

We start with the first power, 10^6. In the A and D part:

$\begin{gathered} 69,000,000-(2.7\cdot10^6) \\ =69,000,000-(2.7\cdot1,000,000) \\ =69,000,000-2,700,000 \\ =66,300,000\ne42,000,000 \\ \\ (6.6\cdot10^6)-150,000 \\ =6,600,000-150,000 \\ =6,450,000\ne64,500,000 \end{gathered}$

then, both are incorrect.

We have 10^7 in the B and C part:

$\begin{gathered} (7.4\cdot10^7)-3,100,000 \\ =7.4\cdot10,000,000-3,100,000 \\ =74,000,000-3,100,000_{} \\ =70,900,000 \\ \\ 750,000,000-(3.2\cdot10^7) \\ =750,000,000-(3.2\cdot10,000,000) \\ =750,000,000-32,000,000 \\ =718,000,000 \end{gathered}$

We have