Question

Efectuati sumele: a) 1/12+2/12+3/12+........+99/12. b) 2/4+4/8+16/12+.......+280/560

Answer 1

1/12(1+2+3+...+99)=1/12*99*100/2=1/4*33*50=33/4*50=1650/4=412.5       2/4(1+2/2+8/3+....140/140)=1/2*1*2/2=1/2