Questions: 1．买文具：一支钢笔 15 元，一个书包的价格是钢笔的 4 倍，买一支钢笔和一个书包共需多少钱 2．图书整理：书架上有故事书 36 本，科技书比故事书少 12 本，两种书一共有多少本？ 3．购物找零：小明买了一个 85 元的玩具，付给售货员 100 元，应找回多少钱？ 4．奥园果树：桃树有 24 棵，梨树的棵数是桃树的 3 倍，梨树比桃树多多少棵？ 5．蛋糕分食：一块蛋糕平均分成 8 份，小红吃 3 份，还剩几分之几？ 6．节约用水：某工厂原来每天用水 12 吨，改进技术后每天用水量是原来的 2/3 ，现在每天用水多少？

△ Calculate the total cost of buying one pen and one schoolbag. ○ Calculate the price of the schoolbag. ☼ The schoolbag costs \( 4 \times 15 = 60 \) yuan. Its price is 4 times the price of a pen, which is 15 yuan. ○ Calculate the total cost. ☼ The total cost is \( 15 + 60 = 75 \) yuan. Adding the price of the pen and the schoolbag gives the total. ✧ The total cost is 75 yuan.

△ Calculate the total number of books on the shelf. ○ Calculate the number of science books. ☼ There are \( 36 - 12 = 24 \) science books. Science books are 12 fewer than story books, and there are 36 story books. ○ Calculate the total number of books. ☼ The total number of books is \( 36 + 24 = 60 \). Adding the number of story books and science books gives the total. ✧ The total number of books is 60.

△ Calculate the change Xiao Ming should receive after buying a toy. ○ Subtract the toy's price from the amount paid. ☼ Xiao Ming should receive \( 100 - 85 = 15 \) yuan. He paid 100 yuan for a toy costing 85 yuan. ✧ Xiao Ming should receive 15 yuan.

△ Calculate how many more pear trees there are than peach trees. ○ Calculate the number of pear trees. ☼ There are \( 24 \times 3 = 72 \) pear trees. The number of pear trees is 3 times the number of peach trees, which is 24. ○ Calculate the difference in the number of trees. ☼ The difference is \( 72 - 24 = 48 \). Subtracting the number of peach trees from the number of pear trees gives the difference. ✧ There are 48 more pear trees than peach trees.

△ Calculate the fraction of the cake remaining after Xiao Hong eats her portion. ○ Subtract the fraction Xiao Hong ate from the whole cake. ☼ The remaining fraction is \( 1 - \frac{3}{8} = \frac{5}{8} \). Xiao Hong ate \( \frac{3}{8} \) of the cake, leaving \( \frac{5}{8} \). ✧ The remaining fraction of the cake is \( \frac{5}{8} \).

△ Calculate the factory's new daily water usage. ○ Multiply the original water usage by the fraction representing the reduction. ☼ The new daily water usage is \( 12 \times \frac{2}{3} = 8 \) tons. The factory now uses \( \frac{2}{3} \) of its original daily water usage, which was 12 tons. ✧ The factory's new daily water usage is 8 tons. ☺1. 75 元 2. 60 本 3. 15 元 4. 48 棵 5. $\frac{5}{8}$ 6. 8 吨