Long multiplication with partial products
Multiply all of A by each digit of B, starting from the ones digit. Shift each partial product one place further left for each place the digit sits from the right, then add the partial products.
Example: 3,472 × 256. 3,472 × 6 = 20,832; 3,472 × 5 tens = 173,600; 3,472 × 2 hundreds = 694,400. The sum is 20,832 + 173,600 + 694,400 = 888,832.
Long addition and subtraction
Addition works from the ones column leftward. If a column adds to 10 or more, write its last digit and carry 1. For 478 + 356: 8 + 6 = 14, write 4 and carry 1; 7 + 5 + 1 = 13, write 3 and carry 1; 4 + 3 + 1 = 8. The answer is 834.
Subtraction borrows (regroups) when a top digit is smaller than the digit below it. For 5,003 − 1,247, the ones, tens and hundreds columns each borrow, giving 3,756. If B is larger than A, the calculator subtracts A from B and makes the answer negative.
Limits
The arithmetic is exact, with no rounding. Multiplication accepts up to 200 digits in A and 40 in B, so there is one partial product per digit of B. Addition and subtraction accept whole numbers or decimals of up to 200 digits that are zero or positive; use signed numbers mode for negative values. Lattice mode takes whole numbers of up to 20 digits each.
Decimals and lists of numbers
To add or subtract decimals, line up the decimal points, pad the shorter numbers with zeros, and work column by column as with whole numbers. For 12.5 + 7.25 + 100 + 0.375, pad to three places (12.500, 7.250, 100.000, 0.375) and add to get 120.125. Choose "A list of numbers" to add up to 50 numbers at once.
To multiply decimals, ignore the points and multiply the digits, then count the decimal places in both factors. For 3.25 × 1.4, 325 × 14 = 4,550, and 2 + 1 = 3 places gives 4.550 = 4.55.
Adding and subtracting signed numbers
Signed numbers mode first rewrites subtraction as adding the opposite: A − B = A + (−B). With the same signs, add the absolute values and keep the sign, so −4 + (−6) = −10. With different signs, subtract the smaller absolute value from the larger and keep the sign of the number farther from zero, so −8 + 5 = −3.
On a number line, start at A and move |B| units right when adding a positive number, or left when adding a negative one. For −7 − (−10) = −7 + 10, start at −7 and move 10 right to land on 3.
Lattice multiplication
Lattice (grid) multiplication writes the digits of A across the top of a grid and the digits of B down the right side. Each cell holds the product of its two digits, with the tens above a diagonal line and the units below it.
Add along each diagonal from the bottom right, carrying into the next diagonal, and read the digits around the left and bottom edges. For 23 × 45 the cells are 08, 12, 10 and 15. The diagonal sums are 5, 3 and 10 (write 0, carry 1), and then 0 + 1 = 1, so the product is 1,035.