What is 4.21 as a fraction in simplest form?

To convert 4.21 to a fraction, we first note that the decimal point is after the hundredths place. So, we can write 4.21 as 421/100. To simplify this fraction, we divide the numerator and denominator by their greatest common divisor, which is 1. Therefore, 4.21 as a fraction in simplest form is 421/100.