Răspuns:

Explicație pas cu pas:

a) 16*3/8 = 6

b) 64*5/4 = 80

c) 21*4/5 = 16,8

d) 147*16/7 = 336

e) 1524*0/4 = 0

f) 60*2/3 = 40 m

g) 60*4/15 = 16 kg

h) 2*5/6 = 10 min/6 = 600 s/6 = 100 s

i)

1 + 2 + 3 + ...+ 20 = 20*21/2 = 10*21

2 + 4 + 6 + ...+ 42 = 2*(1 + 2 + 3 + ...+ 21) = 2*21*22/2 = 22*21

10*21/22*21 = 10/22 = 5/11

66*5/11 = 30

Răspuns:

Explicație pas cu pas:

a) 3/8*16 = 3/2

b) 5/4*64 = 5*16 = 80, pt. ca 5/4 >  1

c) 4/5*21 = 84/5

d) 16/7*147 = 16*21 = 336,  16/7 > 1

e) 0/4*1524 = 0

f) 2 min = 2*60 = 120 sec

5/6*120 = 5*20 = 100 sec = 1'40"

i) 1+2+3+...+20 = 20*21/2 = 10*21

2+4+6+...+42 = 2(1+2+3+...+21) =

2*21*22/2 = 21*22

10*21/21*22 = 10/22 = 5/11

5/11*66 = 5*6 = 30