27/140+27/280+27/420+27/560+27/700+27/840
Fiecare fractie are acelasi numarator[27] si numitori diferiti ,ce rezulta ca numaratorul va ramane acelasi ,iar numitorii se vor aduna intre ei.
⇒27/140+280+420+560+700+840
⇒27/420+420+560+700+840
⇒27/840+560+700+840
⇒27/1400+700+840
⇒27/2100+840
⇒27/2940=9/980;
1/11×1/7+1/11×1/14+1.11×1/21
⇒1/11[1/7+1/14+1/21]
⇒1/11[2/14+1/14+1/21]
⇒1/11[3/14+1/21]
⇒1/11[9/42+2/42]
⇒1/11[11/42]
⇒1/11×11/42
⇒1/42;
