Calcul Fractionnaire

a) $\dfrac{32}{6} = \dfrac{16 \times 2}{3 \times 2} = $ $\dfrac{16}{3}$

b) $\dfrac{54}{18} = \dfrac{3 \times 18}{1 \times 18} = $ $3$

c) $\dfrac{45}{20} = \dfrac{9 \times 5}{4 \times 5} = $ $\dfrac{9}{4}$

d) $\dfrac{44}{11} = \dfrac{4 \times 11}{1 \times 11} = $ $4$

e) $\dfrac{28}{21} = \dfrac{4 \times 7}{3 \times 7} = $ $\dfrac{4}{3}$

a) On divise par 12 : $\dfrac{48 \div 12}{60 \div 12} = $ $\dfrac{4}{5}$

b) On divise par 11 : $\dfrac{33 \div 11}{77 \div 11} = $ $\dfrac{3}{7}$

c) On multiplie par 3 : $\dfrac{5 \times 3}{7 \times 3} = $ $\dfrac{15}{21}$

d) On multiplie par 20 : $\dfrac{4 \times 20}{5 \times 20} = $ $\dfrac{80}{100}$

e) On divise par 3 : $\dfrac{27 \div 3}{15 \div 3} = $ $\dfrac{9}{5}$

On met tout sur le dénominateur commun 150 :

• $\dfrac{22}{15} = \dfrac{220}{150}$
• $\dfrac{3,7}{1,5} = \dfrac{37}{15} = \dfrac{370}{150}$
• $\dfrac{9}{5} = \dfrac{270}{150}$
• $\dfrac{434}{150}$
• $\dfrac{43}{15} = \dfrac{430}{150}$

On compare les numérateurs : $434 > 430 > 370 > 270 > 220$.

Donc : $\dfrac{434}{150} > \dfrac{43}{15} > \dfrac{3,7}{1,5} > \dfrac{9}{5} > \dfrac{22}{15}$

A = $\dfrac{42}{14} \times 15 = 3 \times 15 = $ 45

B = $\dfrac{44}{11} \times 100 = 4 \times 100 = $ 400

C = $\dfrac{25}{5} \times 7 = 5 \times 7 = $ 35

D = $\dfrac{12}{6} \times 5 = 2 \times 5 = $ 10

E = $\dfrac{63}{9} \times 10 = 7 \times 10 = $ 70

A = $\dfrac{3 \times 8}{4 \times 9} = \dfrac{3 \times 4 \times 2}{4 \times 3 \times 3} = $ $\dfrac{2}{3}$

B = $\dfrac{10 \times 21}{7 \times 5} = \dfrac{2 \times 5 \times 7 \times 3}{7 \times 5} = 2 \times 3 = $ 6

C = $\dfrac{35}{24} \times \dfrac{8}{7} = \dfrac{7 \times 5 \times 8}{8 \times 3 \times 7} = $ $\dfrac{5}{3}$

D = $\dfrac{49 \times 16}{64 \times 63} = \dfrac{7 \times 7 \times 16}{16 \times 4 \times 7 \times 9} = $ $\dfrac{7}{36}$

E = $\dfrac{5 \times 13 \times 8}{2 \times 5} = \dfrac{13 \times 2 \times 4}{2} = 13 \times 4 = $ 52