3. จงหาผลคูณ
1) (11 x 3) x 7
วิธีทำ
(11 x 3) x 7
= 33 x 7
= 231
ตอบ 231
2) 11 x (3 x 7)
วิธีทำ
11 x (3 x 7)
= 11 x 21
= 231
ตอบ 231
3) [5 x (-8)] x 4
วิธีทำ
[5 x (-8)] x 4
= [-(5 x 8)] x 4
= (-40) x 4
= -(40 x 4)
= -160
= -(40 x 4)
= -160
ตอบ -160
4) 5 x [(-8) x 4]
วิธีทำ
5 x [(-8) x 4]
= 5 x [-(8 x 4)]
= 5 x (-32)
= -(5 x 32)
= -160
= -(5 x 32)
= -160
ตอบ -160
5) -10[6(-3)]
วิธีทำ
-10[6(-3)]
= -10[-(6(3))]
= -10(-18)
= 10(18)
= 180
= 10(18)
= 180
ตอบ 180
6) [(-10)6](-3)
วิธีทำ
[(-10)6](-3)
= [-((10)6)](-3)
= (-60)(-3)
= (60)(3)
= 180
= (60)(3)
= 180
ตอบ 180
7) (-7)[(-4) · (-6)]
วิธีทำ
(-7)[(-4) · (-6)]
= (-7)(4 · 6)
= (-7)(24)
= -[(7)(24)]
= -168
= -[(7)(24)]
= -168
ตอบ -168
8) [-7(-4)] · (-6)
วิธีทำ
[-7(-4)] · (-6)
= [7(4)] · (-6)
= 28 · (-6)
= -(28 · 6)
= -168
= -(28 · 6)
= -168
ตอบ -168
9) [(-13)(-5)] x (-20)
วิธีทำ
[(-13)(-5)] x (-20)
= [(13)(5)] x (-20)
= 65 x (-20)
= -(65 x 20)
= -1,300
= -(65 x 20)
= -1,300
ตอบ -1,300
10) -13[(-5) x (-20)]
วิธีทำ
-13[(-5) x (-20)]
= -13[(5)(20)]
= -13(100)
= -[13(100)]
= -1,300
= -[13(100)]
= -1,300
ตอบ -1,300