Without using a calculator we can multiply 194340 by 8 and divide the result by 1000 (move decimal point three places to the left.
We can double 194340 three times then shift the decimal point 3 places to the left:
388680 (multiply by 2)
777360 (multiply by 2 again)
1554720 (multiply by 2 again)
1554.72 (move decimal point 3 places to the left)