扬帆起航
$1.36-0.58=$ $10.71-9.85=$ $5.4-0.9=$
$2.73-0.34=$ $6.81-5.19=$ $7-4.36=$
$8.65-5=$ $4.15-3=$ $7.68-1.89=$
$7.86-4.9=$ $10-7.76=$ $0.67-0.39=$

1. $1.36 - 0.58 = 0.78$
$\begin{array}{r}1.36\\- 0.58\\\hline0.78\end{array}$
2. $10.71 - 9.85 = 0.86$
$\begin{array}{r}10.71\\-9.85\\\hline0.86\end{array}$
3. $5.4 - 0.9 = 4.5$
$\begin{array}{r}5.4\\-0.9\\\hline4.5\end{array}$
4. $2.73 - 0.34 = 2.39$
$\begin{array}{r}2.73\\-0.34\\\hline2.39\end{array}$
5. $6.81 - 5.19 = 1.62$
$\begin{array}{r}6.81\\-5.19\\\hline1.62\end{array}$
6. $7 - 4.36 = 2.64$
$\begin{array}{r}7.00\\-4.36\\\hline2.64\end{array}$
7. $8.65 - 5 = 3.65$
$\begin{array}{r}8.65\\-5.00\\\hline3.65\end{array}$
8. $4.15 - 3 = 1.15$
$\begin{array}{r}4.15\\-3.00\\\hline1.15\end{array}$
9. $7.68 - 1.89 = 5.79$
$\begin{array}{r}7.68\\-1.89\\\hline5.79\end{array}$
10. $7.86 - 4.9 = 2.96$
$\begin{array}{r}7.86\\-4.90\\\hline2.96\end{array}$
11. $10 - 7.76 = 2.24$
$\begin{array}{r}10.00\\-7.76\\\hline2.24\end{array}$
12. $0.67 - 0.39 = 0.28$
$\begin{array}{r}0.67\\-0.39\\\hline0.28\end{array}$

乘风破浪
$7.35+0.8=$ $5.39+0.6=$ $1.98+0.52=$
$6.5+0.49=$ $4.35+0.27=$ $8.56+0.99=$
$6.24+7.19=$ $8.39+4.39=$ $3.75+6.92=$
$77.4+0.98=$ $9.59+3.8=$ $45.6+1.87=$
$55+7.6=$ $0.3+0.98=$ $50+4.96=$
$6.7+2.9=$ $9.8+2.4=$ $8.3+7.9=$
$2.27-1.37=$ $7.48-0.78=$ $6.62+0.38=$
$78+24.7=$ $6.83+4.99=$ $77.38+0.96=$

$7.35+0.8=8.15$
$5.39+0.6=5.99$
$1.98+0.52=2.5$
$6.5+0.49=6.99$
$4.35+0.27=4.62$
$8.56+0.99=9.55$
$6.24+7.19=13.43$
$8.39+4.39=12.78$
$3.75+6.92=10.67$
$77.4+0.98=78.38$
$9.59+3.8=13.39$
$45.6+1.87=47.47$
$55+7.6=62.6$
$0.3+0.98=1.28$
$50+4.96=54.96$
$6.7+2.9=9.6$
$9.8+2.4=12.2$
$8.3+7.9=16.2$
$2.27-1.37=0.9$
$7.48-0.78=6.7$
$6.62+0.38=7$
$78+24.7=102.7$
$6.83+4.99=11.82$
$77.38+0.96=78.34$

圆满返航
两个数相加的和是$8.57$，如果一个加数增加$6.43$，另一个加数减少$7.5$，那么此时的和变为多少？
秘籍点拨 加数增加，和会怎么变化？加数减少，和又会怎么变化？

原来两数之和为$8.57$，
一个加数增加$6.43$，和增加$6.43$，
另一个加数减少$7.5$，和减少$7.5$，
变化后的和：
$8.57+6.43-7.5$
$=15-7.5$
$=7.5$
答：此时的和变为$7.5$。