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10) 991 x 999 = (99 x 100)’09 = 990009

8.1.5 Menghitung perkalian dari 2 bilangan ribuan dengan
jumlah ke dua bilangan satuannya sepuluh.

1) 1115 x 1115 = (111 x 112)’25 = 12.432.225

2) 1114 x 1116 = (111 x 112)’24 = 12.432.224

3) 1113 x 1117 = (111 x 112)’21 = 12.432.221

4) 1112 x 1118 = (111 x 112)’16 = 12.432.226

5) 1111 x 1119 = (111 x 112)’09 = 12.432.229
6) 9995 x 9995 = (999 x 1000)’25 = 99900025

7) 9994 x 9996 = (999 x 1000)’24 = 99900024
8) 9993 x 9997 = (999 x 1000)’21 = 99900021

9) 9992 x 9998 = (999 x 1000)’16 = 99900016

10) 9991 x 9999 = (999 x 1000)’09 = 99900009

8.2.6 Perkalian dua digit dengan satuan 8 (Cara lain)

1) 18 x 18 = 20.20 – 2.2.20 + 2.2 = 400 – 76 = 324 atau

18 x 18 = 20.20 – 4.20 + 4 = 400 – 76 = 324

2) 28 x 28 = 30.30 – 4.30 + 4 = 900 – 116 = 784

3) 38 x 38 = 40.40 – 4.40 + 4 = 1600 – 156 = 1444

4) 48 x 48 = 50.50 – 4.50 + 4 = 2500 – 196 = 2304

5) 58 x 58 = 60.60 – 4.60 + 4 = 3600 – 236 = 3364

6) 68 x 68 = 70.70 – 4.70 + 4 = 4900 – 276 = 4624

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