Try some simple memorization exercises. For instance, have your child memorize the multiples of two, from two to 20. Learning disabilities can interfere with a child's ability to memorize simple sequences and students with dyscalculia will find it exceedingly difficult to keep the numbers in order, especially sequences that skip numbers (2, 4, 6, 8, 10, for instance).
Ask your child to read you a story. Math learning disabilities can be caused by language problems or visual issues, so if your child has difficulty reading words as well as numbers they may need to see a physician.
Say a math problem aloud, and have your child write it down. Some math learning disabilities make it difficult for children to organize the numbers and signs in an equation.
Speak with the child about his school experiences. If he is having trouble with math or other subjects, you may be able to spot a problem simply by asking him about what has been going on in his social life and coursework.
Consult your child's math teacher and find out if your child is struggling with specific areas of her studies, or in all categories. Teachers are on the front lines with students every day and may be able to spot a learning disability based on previous students.
Watch your child's behavior for signs of number-related struggles. Kids with dyscalculia and similar learning disabilities will likely have difficulty with concepts like money and simple directions from one point to another.