Mark the boxes that have the correct results of the operations that appear in the clouds and write down the secret word that results by joining the unmarked letter of each train car.

Each train car has four boxes, each with a number and a letter. The number corresponds to the possible response of an addition. The sums are the clouds above each car. Since there are only three sums and four boxes, one of the boxes of each car will not be crossed out. The letters of all these boxes will form a 6-letter word. Discover the word and confirm your work!

Children are very interested in discovering what the hidden word is and that helps to motivate them to complete the exercises.

Since the options of possible results in the boxes are limited, students can **check their own work** by logic and a process of elimination. **Another form** of feedback is to make sure that the letters of the spared boxes form a word. **A third way** is to give the same worksheet to several boys and girls so that they can see that they have the same words.

Each worksheet contains two trains, and each train contains 18 operations. The document contains worksheets with exercises and a very attractive theme and is in PDF format. Use the password **worksheets.site** to open the PDF file.

One way of working with these resources can be to print and assign the same worksheet for every students and easily verify the next day that the children have found the secret words. Or they could also be a group activity to discuss which boxes to cross out. In a group of three students each one could be responsible of an operation per train car and discover the spared box collaboratively.