There are experts who can add very rapidly. The best of them, however, cannot add up a column of _ones_ any faster than you can. Here is how some of the rapid addition is performed. The operator writes a line of figures, then another, and so on. The second line, however, added to the first makes _nines_, except at the extreme right, where the two figures add to _ten_. The third and fourth bear the same relation, and as many more as he chooses to put down. The last two lines, however, are put down at random. Now, to add these columns, he begins anywhere, perhaps at the left-hand side, putting down 2 (the number of _pairs_ above), then by simply adding the two bottom lines, he gets the correct sum. Bank Discount. The sum charged by a bank for cashing a note or time draft is called bank discount. This _discount_ is the simple interest, paid in advance, for the number of days the note has to run. Wholesale business houses usually sell goods on time and take notes from the retailers in payment. These notes are not often for a longer period than three months. Some are placed in the banks for _collection_, others are discounted. When a note is discounted at a bank the _payee_ endorses it, making it payable to the bank. Both maker and payee are then responsible to the bank for its payment. If the note is drawing interest the discount is reckoned on and deducted from the amount due at maturity. Most notes discounted at banks do not draw interest. The time in bank discount is always the number of days from the _date of discounting_ to the _date of maturity_. Example. A note of $250, dated July 7th, payable in 60 days, is discounted July 7th, at 6 per cent.; find the proceeds. This note is due in 63 days, or September 8th. The accurate interest of $250 for 63 days at 6 per cent. is $2.59. The proceeds, then, will be $250 - $2.59, or $247.41. How to Make Change. Salesmen usually make change by addition. They have the money to count out, and in doing so they add to the amount of the purchase until they reach the amount of the bill presented. For example, if you buy something worth $3.35 and present a ten-dollar bill in payment, you will probably receive in return 5 cents, 10 cents, 50 cents, $1, and $5; the salesman saying 40, 50, $4, $5; $10. This method is least liable to error. Accuracy and rapidity in counting out change can best be acquired by practice behind the counter or at the cash-desk. Proof of Multiplication in Ten Seconds. The _unitate_ of a number is the sum of its digits reduced to a unit. 252 = 9 } = 54 = 9 321 = 6 } --- 252 504 756 ----- 80892 = 27 = 9 The _unitate_ of the multiplier is 9 and the _unitate_ of the multiplicand is 6; 6 times 9 equals 54, and the _unitate_ of 54 is 9. Now the _unitate_ of the product is found to be 9 also, which is a proof of the correctness of the work. The Canadian Interest Rule. 4 | 724 181 × 11 = 19.91