0.25 × 1.8 + 3.9 (simple calculation)

0.25 × 1.8 + 3.9 (simple calculation)

0.25×1.8+3.9
=0.3*(0.25*6+1.3)
=0.3*(1.5+1.3)
=0.3*2.8
=0.3*(3-0.2)
=0.9-0.06
=0.84

Simple calculation of 399.6 × 9-1998 × 0.8
399.6×9-1998×0.8
Simple calculation, formula as little as possible, to be able to understand

399.6×9-1998×0.8
=199.8x2x9-199.8x8
=199.8x(18-8)
=199.8x10
=1998
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98-102 / 6.8 with [simple calculation] 43.27 * 7.9 + 2.1 * 43.27

98-102÷6.8
=98-15
=83
43.27×7.9+2.1×43.27
=43.27×(7.9+2.1)
=43.27×10
=432.7

42 × 98, the first adopted

41.16