Can we choose seven of these nine numbers so that the sum is 50? 1, 3, 5, 7, 7, 9, 11, 15, 21
Six numbers, 21 + 3 + 5 + 11 + 9 + 1 = 50 or
In 1 / 3, 1 / 2, 5 / 9, 7 / 12, 9 / 15, 11 / 18, the 50th number is ()
First restore these scores, and the law will come out,
It's very simple. 1 / 3, 3 / 6, 5 / 9. The key is to change 1 / 2 into 3 / 6. Then, those who have learned induction can see it very quickly. The general formula is (2n-1) / (3n), where n is a natural number. Just substitute 50 for it. 99 / 150, that is 33 / 50
3.15.9.7.21.1.5.11.7 select 7 numbers to make their sum 50
3+15+9+7+21+1+5+11+7=79
79-50=29
impossible
3.6X2.7+18X0.56-1.8X10%÷10%
Off formula calculation! Can be simple to calculate!
3.6X2.7+18X0.56-1.8X10%÷10%
1.8x 5.4 + 1.8x 5.6 - 1.8 x 1
= 1.5x ( 5.4 + 5.6 -1)
= 1.5 x 10
= 15