Explanation:
if you multiply something by 10 = 10¹, you move the decimal point 1 position to the right (and fill up with a 0, if necessary).
if you multiply something by 100 = 10², you move the decimal point 2 positions to the right (and fill up with 0s as needed).
if you multiply something by 1000 = 10³, you move the decimal point 3 positions to the right (and fill up with 0s as needed).
...
you see the pattern ?
so, when multiplying by 10⁵ (100,000) we shift the decimal point 5 pairings to the right and fill up with 0s as needed.
therefore,
7.9 × 10⁵ = 790,000.-