三年级采集了12.4千克树种,四年级采集的比三年级的少2.1千克,两个年级一共采集了多少千克树种?
计算,怎样算简便就怎样算102×(4.5÷0.09) 19.96×5.4﹣4.4×19.96 3.8+2.49+7.51+4.22.3+3.91÷(22﹣19.7) (1﹣0.2)×[13﹣(3.12+5.28)] 9.9×1.45.
递等式计算,能简算的要简算.4.8×0.25 2.33×0.5×4 1.2×2.5+0.8×2.550.4×1.9﹣1.9 3.7×0.25+4 0.65×201.
用脱式计算.(除不尽时四舍五入保留两位小数)①13.7×0.25×8 ②18﹣(1.4+1.25×2.4)③(10.5+27.8)÷(5.2﹣2.5) ④4.2÷[8×(6.34﹣4.59)].
脱式计算.(能简算的要简算)7.02×1.02 1.125÷0.092001×0.54+2001×0.46 0.64×0.25+0.750.78÷26+0.5×0.02 [2.8﹣2.8×(2.8﹣2.8)]÷0.78×[1÷(3.2﹣2.95)] 33.4﹣26.465÷(2.6+4.1)
脱式计算,(能简算的要简算)25×7.6×0.8 23.7﹣3.9+6.3﹣6.1 2.5×64×1.25.1÷(1﹣0.98) 5.9×7.8+5.9×1.2+5.9 26.8×0.25﹣6.8÷4.