1. จงหาผลลัพธ์
1) (-420) ・ [39 + (-40)]
วิธีทำ
(-420) ・ [39 + (-40)]
= (-420)・[-(40 – 39)]
= (-420)・(-1)
= 420・1
= 420
= 420・1
= 420
ตอบ 420
2) [(-27) – (-27)] x (-582)
วิธีทำ
[(-27) – (-27)] x (-582)
= [(-27) + 27] x (-582)
= 0 x (-582)
= 0
= 0
ตอบ 0
3) [(-24) – (-24)] \(\div\) (-50)
วิธีทำ
[(-24) – (-24)] \(\div\) (-50)
= [(-24) + 24] \(\div\) (-50)
= 0 \(\div\) (-50)
= 0
= 0
ตอบ 0
4) 199 \(\div\) [17 + (-18)]
วิธีทำ
199 \(\div\) [17 + (-18)]
= 199 \(\div\) [-(18 – 17)]
= 199 \(\div\) (-1)
= -(199 \(\div\) 1)
= -199
= -(199 \(\div\) 1)
= -199
ตอบ -199
5) (-23 x 10) + (22 x 10)
วิธีทำ
(-23 x 10) + (22 x 10)
= [(-23) + 22] x 10
= [-(23 – 22)] x 10
= (-1) x 10
= -(1 x 10)
= -10
= (-1) x 10
= -(1 x 10)
= -10
ตอบ -10
6) (-4 x 13) – (9 x 13)
วิธีทำ
(-4 x 13) – (9 x 13)
= [(-4) – 9] x 13
= [(-4) + (-9)] x 13
= [-(4 + 9)] x 13
= (-13) x 13
= -(13 x 13)
= -169
= [-(4 + 9)] x 13
= (-13) x 13
= -(13 x 13)
= -169
ตอบ -169
7) [(-9)(-5)] – [(-9)(-12)]
วิธีทำ
[(-9)(-5)] – [(-9)(-12)]
= (-9)[(-5) – (-12)]
= (-9)[(-5) + 12]
= (-9)(12 – 5)
= (-9)(7)
= -[(9)(7)]
= -63
= (-9)(12 – 5)
= (-9)(7)
= -[(9)(7)]
= -63
ตอบ -63
8) 97 x 15
วิธีทำ
97 x 15
= (100 – 3) x 15
= (100 x 15) – (3 x 15)
= 1,500 – 45
= 1,455
= 1,500 – 45
= 1,455
ตอบ 1,455
9) -12 x 198
วิธีทำ
-12 x 198
= -12 x (200 – 2)
= [(-12) x 200] – [(-12) x 2]
= [-(12 x 200)] – [-(12 x 2)]
= (-2,400) – (-24)
= (-2,400) + 24
= -(2,400 – 24)
= -2,376
= [-(12 x 200)] – [-(12 x 2)]
= (-2,400) – (-24)
= (-2,400) + 24
= -(2,400 – 24)
= -2,376
ตอบ -2,376
10) (-496) x (-25)
วิธีทำ
(-496) x (-25)
= 496 x 25
= (500 – 4) x 25
= (500 x 25) – (4 x 25)
= 12,500 – 100
= 12,400
= (500 x 25) – (4 x 25)
= 12,500 – 100
= 12,400
ตอบ 12,400