一、下表中哪些是 20 的因数,哪些是 15 的因数？在相应的格子里画
| | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| 20 的因数 | | | | | | | | | | |
| 15 的因数 | | | | | | | | | | |
| | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 |
| 20 的因数 | | | | | | | | | | |
| 15 的因数 | | | | | | | | | | |
根据上表按要求把数填在下面的圈内。

| | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| 20 的因数 | √ | √ | | √ | √ | | | | | √ |
| 15 的因数 | √ | | √ | | √ | | | | | |
| | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 |
| 20 的因数 | | | | | | | | | | √ |
| 15 的因数 | | | | | √ | | | | | |
$20$的因数：$2$、$4$、$10$、$20$；$15$的因数：$3$、$15$；$20$和$15$的公因数：$1$、$5$。
故$20$的因数圈填$2$、$4$、$10$、$20$；$15$的因数圈填$3$、$15$；相交部分（公因数）填$1$、$5$。

二、投篮。

$\frac{1}{3}$与$\frac{12}{36}$、$\frac{13}{39}$、$\frac{5}{15}$、$\frac{8}{24}$、$\frac{6}{18}$相连；$\frac{1}{2}$与$\frac{13}{26}$、$\frac{10}{20}$、$\frac{25}{50}$、$\frac{9}{18}$、$\frac{7}{14}$相连。

三、八种图形中,有哪几种可以制成与右边立体图相同的正方体？

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