its the same as 1.25, we know that 1/4th is the same as .25 just think about money a dollar is $1.00, 75 cent is 3/4th of a dollar, 50 cent is 1/2, 25 cent is 1/4th.
another way we can do this and THIS WORKS FOR ALL MIXED FRACTIONS, is to multiply the whole number by the deminator, and add the numerator, use the same deminator in your fraction
1 1/4= 4 x 1 = 4 + 1 = 5 1 1/4 is the same as 5/4 or 1.25