Question

[Phạm Hà Linh]

Tính hợp lí:
a) 120.15 + 12.470 + 12.38.10 b) 13.58.4 + 32.26.2 + 52.10
c) 3,2.990 + 32 d) 45. (13 + 78) + 9. (87 + 22).5
e) (24 + 72 + 36 + 60) : 12
f) (2 + 4 + 6 + … + 100). (36.333 – 108.111)

Answer 1

[trương khoa]

a, \(120\cdot15+12\cdot470+12\cdot38\cdot10\)

\(=12\cdot10\cdot15+12\cdot47\cdot10+12\cdot38\cdot10\)

\(=120\left(15+47+38\right)=120\cdot100=12000\)

f,\(\left(2+4+6+...+100\right)\cdot\left(36\cdot333-111\cdot108\right)\)

\(=\left(2+4+6+...+100\right)\cdot\left(36\cdot111\cdot3-111\cdot108\right)\)

\(=\left(2+4+6+...+100\right)\cdot111\cdot\left(36\cdot3-108\right)\)

\(=\left(2+4+6+...+100\right)\cdot111\cdot\left(108-108\right)\)

\(=\left(2+4+6+...+100\right)\cdot111\cdot0=0\)

Answer 2

[Lê Hoàng Nhật]

a)
120.15+12.470+12.38.10

=120.15+120.47+120.38=120(15+47+38)=120.100=12000

b)

13.58.4+32.26.2+52.10

=52.58+52.26+52.10=52.(58+26+10)=52.100=5200

c)

3,2.990+32=32.99+32=32.(99+1)=32.100=3200

d)

45.(13+78)+9.(87+22).5

=45.91+45.109=45.(91+109)=45.200=9000

e)

(24+72+36+60):12=12.(2+6+3+5):12=16

f)(2+4+6+...+100)(36.333−108.111)

=(2+4+6+...+100)(36.3.111−36.3.111)=(2+4+6+...+100).0=0