Answer :
Multiplication:-
a. 7/3 × 2/9 = 7x2/3x9 = 14/27.
b. 3/7 × 5/11 = 3×5/7×11 = 15/77.
c. 15/8 × 6/25 = 3×3/4×5 = 9/20.
d. 21/20 × 15/14 = 3×3/4×2 = 9/8.
Division:
a. 3/4 ÷ 5/7 = 3/4 x 7/5 = 21/12 = (3 x 7) / (3 x 4) = 7/4
b. 9/5 ÷ 6/11 = 9/5 x 11/6 = 99/30 = (3 x 33) / (3 x 10) = 33/10
c. 15/8 ÷ 6 = 15/8 x 1/6 = 15/48 = (3 x 15) / (3 x 16) = 15/16
d. 8/7 ÷ 12 = 8/7 x 1/12 = 8/84 = (4 x 2) / (4 x 21) = 2/21.
Culcul constant des fractions:
a. 3/7 + 15/7 x 3/2
= 3/7 + 45/14
= (3 x 2) / (7 x 2) + 45/14
= 6/14 + 45/14
= 51/14
b. 9/5 x (1/4 - 5/12)
= 9/5 x [(1 x 3) / (4 x 3) - 5/12]
= 9/5 x (3/12 - 5/12)
= 9/5 - 2/12
= (9 x 12) / (5 x 12) - (2 x 5) / (12 x 5)
= 108/60 - 10/60
= 98/60
= (2x 49) / (2 x 30)
= 49/30.
c. (3/8 + 7/5) ÷ (9/4 - 5/3)
= [(3 x 5) / (8 x 5) + (7 x 8) / (5 x 8)] ÷ [(9 x 3) / (4 x 3) - (5 x 4) / (3 x 4)]
= (15/40 + 56/40) ÷ (24/12 - 20/12)
= 71/40 ÷ 4/12
= 71/40 x 12/4
= 852/160
= (4 x 213) / (4 x 40)
= 213/40.
Hope this helps..