Question

Answer 1

3:

\(\dfrac{1}{6}+\dfrac{1}{12}+...+\dfrac{1}{90}\)

\(=\dfrac{1}{2\cdot3}+\dfrac{1}{3\cdot4}+...+\dfrac{1}{9\cdot10}\)

\(=\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+...+\dfrac{1}{9}-\dfrac{1}{10}\)

\(=\dfrac{1}{2}-\dfrac{1}{10}=\dfrac{4}{10}=\dfrac{2}{5}\)

1:

\(2012+1320:\left(x+24\right)=2023\)

=>\(\dfrac{1320}{x+24}=2023-2012=11\)

=>x+24=120

=>x=96

2:

31/2=15,5

\(16\dfrac{1}{5}=16,2\)

15,5<15,98<16,2<16,5

=>\(\dfrac{31}{2}< 15,98< 16\dfrac{1}{5}< 16,5\)