Question

Calculati:

a)5supra21-3supra14+2supra7=

b)9supra20+7supra10-2supra15=

c)11supra20-(1supra4+1supra5)

Answer 1

a) cmmmc ( 21,14,7) =2×3×7=42
5/21 - 3/14 +2/7 =     → aducem fractiile la acelasi numitor
=10/42 - 9/42 + 12/42=
=1/42 + 12/42=
=13/42

b)  cmmmc ( 20, 10, 15) =2²²×3×5= 60
9/20+7/10 - 2/15=
=27/60 + 42/60 - 8/60=
=61/60=
=1 intreg si 1/60



c)
11/20 - ( 1/4 + 1/5)=
=11/20 - ( 5/20 + 4/20)=
=11/20 - 9/20 =
=2/20=
=1/10