Question

S=60 + 66 + 72 +…+180 URGENY VA ROG

Answer 1

Răspuns:

S = 6(10+11+12+...+30)

10+11+12+...+30=(30×31)/2 - (9×10)/2 = 465 - 45 = 420

S = 420×6 = 2520

Answer 2

n=(180-66):6+1

n=114:6+1

n=19+1

n=20

S=(180+60)×20:2

S=240×20:2

S=240:2×20

S=120×20

S=2400