Hard Addition: long sums crossword

About Hard Addition

Hard Addition is a math crossword where the clues aren't words but long addition problems with 2, 3 and 4 digits. Each result takes up a row or a column of the board and, as in any crossword, the squares intersect: if you get one sum wrong, you'll notice it in the one next to it. It's a different way to practice calculation that fits very well with our online crosswords.

For families and teachers it's a very useful resource: it turns the typical worksheet of addition with carrying into a pastime, and the crossword sum format encourages checking results instead of writing down the first number that comes to mind.

How do you play Hard Addition?

Each slot in the crossword has a sum attached that appears at the bottom of the screen.

1. Move the mouse (or tap) over an empty row or column of the crossword.
2. Read the proposed sum shown below and solve it, in your head or on paper.
3. Type the result digit by digit in the corresponding squares.
4. When you complete the board, check that everything is correct and press the arrow to move on to a new challenge.

Hard Addition controls

PC

• Mouse: choose the row or column and see its sum
• Numeric keypad or on-screen buttons: enter the digits of the result

Mobile and tablet

• Tap the screen: select squares and type the numbers

What do you learn in Hard Addition?

• Solving two-, three- and four-digit sums with and without carrying.
• Correctly placing units, tens, hundreds and thousands.
• Doing mental math and estimating whether a result is reasonable.
• Self-correcting by using the crossing squares as a check.

Recommended from age 7, when carrying in addition is covered in primary school.

Tips for playing better: Hard Addition

• Start with the shortest sums: their digits fill squares that later serve as clues for the longer ones.
• If you have doubts, do the sum vertically on paper, lining up the digits on the right.
• Before writing, estimate the result by rounding (for example, 5065 + 84 gives a bit more than 5100). That way you'll catch big errors right away.
• When a crossed square doesn't match your result, check the carrying: it's usually the cause of the mistake.

Hard Addition FAQ

What are hard or long sums?

They are sums with multi-digit numbers, usually three or four digits, where you have to carry from one column to the next. In this game, sums with 2, 3 and 4 digits appear.

What grade is this sums crossword for?

It fits second, third and fourth grade of primary school, though it also works as a review for older kids or adults who want to speed up their calculation.

Can I check if the crossword is correct?

Yes. When you finish you can check your answers and then move on to another sums crossword with the next arrow.

Additional information: Hard Addition

Game type: Educational, math sums crossword
Recommended age: From 7 years old
Technology: HTML5
Platform: Web browser (PC, tablet and mobile)

Enjoyed Hard Addition? Also try Greater or Less, Multiples of 4 or 3D Geometric Shapes. Find more Math Games and hundreds of free games online on LudoRex.