Question

a, \(\dfrac{1}{2}+\dfrac{1}{4}+\dfrac{1}{8}+\dfrac{1}{16}\)       b, \(\dfrac{1}{2}+\dfrac{1}{3}+\dfrac{1}{5}\)

Answer 1

\(a,\dfrac{1}{2}+\dfrac{1}{4}+\dfrac{1}{8}+\dfrac{1}{16}=\dfrac{8}{16}+\dfrac{4}{16}+\dfrac{2}{16}+\dfrac{1}{16}=\dfrac{8+4+2+1}{16}=\dfrac{15}{16}\)

\(b,\dfrac{1}{2}+\dfrac{1}{3}+\dfrac{1}{5}=\dfrac{15}{30}+\dfrac{10}{30}+\dfrac{6}{30}=\dfrac{15+10+6}{30}=\dfrac{31}{30}\)

Answer 2

b,12+13+15=1530+1030+630=15+10+630=3130