\(\displaystyle 10^5= 100000\) (the exponent if 5 so there are 5 zeros).

\(\displaystyle 5.42\times 10^5= 5.42\times 100000\).

Move the decimal point in 5.42 to the right five places. Moving it two places gives 542 so three more places is 542000. That is the same as \(\displaystyle 542000\times 1= 542000\times 10^0\).