確認問題4(正の数・負の数)解答・解説
(1) (-8)×(-5)
＝+(8×5)
＝+40
(2) 1.4×(-0.7)
＝-(1.4×0.7)
＝-(9.8)
＝-9.8
(3) (-20)÷4
＝-(20÷4)
＝-(5)
＝-5
(4) (-5/6)÷(-10/9)
＝(-5/6)×(-9/10)
＝+3/4
(5) (-5)×7×(-2)
＝(-5)×(-2)×7
＝(+10)×7
＝+70
＝70
(6) 16÷(-8)×2
＝16×(-1/8)×2
＝-(2)×2
＝-(4)
＝-4
(7) (-9)÷(-2/3)×(-12)
＝(-9)×(-3/2)×(-12)
＝(+27/2)×(-12)
＝-27×6
＝-162
(8) 6÷(-3/5)÷(-2/3)
＝6×(-5/3)×(-3/2)
＝(-10)×(-3/2)
＝+15
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