OPCULATO is a fantastic puzzle designed to enhance mental arithmetic skills. You may look at an OPCULATO puzzle and say to yourself these are too hard. Are they really too hard? Yes maybe they are too hard. The first row certainly isn't. It's actually quiet easy. The second row is also easy. The third row will make you think. It doesn't matter if you don't get the puzzle correct the first time. It's more important that you try and work out the math in your head. The more you practice this type of hard mental training the stronger you will become. One puzzle can take 5 minutes to complete .My advice is to not use a calculator while trying to solve these puzzles. Some rows in the puzzles may have different solutions but the overall puzzle should have one solution as the connecting downward puzzle requires a whole number to be entered in the bottom square.If your getting fractions or decimals in your solution you'll have to change a row. You can try one or two now in the images above. Solutions are provided. This book includes 90 puzzles and 90 solutions. Please support OPCULATO if you like these types of puzzles by buying the book which will help improve OPCULATO website ,games ,books and puzzles and encourage mental arithmetic. The kindle version is not interactive and is an ideal way to practice mental arithmetic by trying to solve one OPCULATO puzzle a day while on a bus,train or relaxing in your own home. Enjoy OPCULATO and never use a calculator and be smart.