2 вариант: вычислите: 1) 2/25 + 1/4; 2) 11/5 + 13/4; 3) (17/16 − 1/32) : 1/24; 4) (12/11 − 17/10) : 5/22; 5) 0,8/(1 + 1/7); 6) 9/(3 · 2); 7) (9/16 + 2 3/8) · 4; 8) 7 · (1/7)² − 8 · 1/7; 9) (4,2)/(8,2 − 7,4); 10) (1,7 + 3,8)/2,2; 11) (2,1 · 3,5)/4,9; 12) 2,5 · 3,5 − 0,35; 13) (5 · 10⁻²)³ − (2 − 10³).

\(\frac{2}{25}+\frac{1}{4}=\frac{8}{100}+\frac{25}{100}=\frac{33}{100}.\)

\(\frac{11}{5}+\frac{13}{4}=\frac{44}{20}+\frac{65}{20}=\frac{109}{20}=5\frac{9}{20}.\)

\(\left(\frac{17}{16}-\frac{1}{32}\right):\frac{1}{24}=\frac{33}{32}\cdot24=\frac{99}{4}=24\frac{3}{4}.\)

\(\left(\frac{12}{11}-\frac{17}{10}\right):\frac{5}{22}=\left(-\frac{67}{110}\right)\cdot\frac{22}{5}=-\frac{67}{25}=-2\frac{17}{25}.\)

\(0{,}8:(1+\frac{1}{7})=0{,}8:\frac{8}{7}=0{,}8\cdot\frac{7}{8}=0{,}7.\)

\(9:(3\cdot2)=9:6=1{,}5.\)

\((\frac{9}{16}+2\frac{3}{8})\cdot4=(\frac{9}{16}+\frac{38}{16})\cdot4=\frac{47}{16}\cdot4=\frac{47}{4}=11\frac{3}{4}.\)

\(7\cdot(\frac{1}{7})^2-8\cdot\frac{1}{7}=\frac{1}{7}-\frac{8}{7}=-1.\)

\(4{,}2:(8{,}2-7{,}4)=4{,}2:0{,}8=5{,}25.\)

\((1{,}7+3{,}8):2{,}2=5{,}5:2{,}2=2{,}5.\)

\((2{,}1\cdot3{,}5):4{,}9=7{,}35:4{,}9=1{,}5.\)

\(2{,}5\cdot3{,}5-0{,}35=8{,}75-0{,}35=8{,}4.\)

\((5\cdot10^{-2})^3-(2-10^3)=0{,}05^3-(-998)=0{,}000125+998=998{,}000125.\)