Exact = 609.
Estimate to 10s = 610.
Estimate to 100s = 600.
2% is 2/100, so we have 2/100*7,000,000,000=140,000,000 people with red hair.
If the decimal is 1 number divide that number into 10 Then simplify the fraction if possible. if the decimal are 2 numbers divide those 2 numbers by 100 Then simplify the fraction if possible
3 numbers:by 1000, etc
Ex 0.4= 4/10 = 2/5