Cross-multiplication technique - two 2- Digit number

cross-multiplication technique - two 2- Digit number

 

"TO MULTIPLY TWO 2-DIGIT NUMBERS 
FIRST             MULTIPLY THE ONES DIGITS TOGETHER,
THEN '            CROSS-MULTIPLY    AND 
FINALLY         MULTIPLY THE TENS DIGITS TOGETHER.

MAKE SURE TO CARRY WHENEVER A PRODUCT EXCEEDS 9. AS YOU WILL SEE IN THE EXAMPLES BELOW, YOU MUST WORK YOUR WAY FROMRIGHT TO LEFT TO PERFORM THIS TRICK.

EX 1:


12 X 23 = ?

1. MULTIPLY THE ONES DIGITS: 2X3=6 (ONES DIGIT ANSWER).
2. CROSS-MULTIPLY AND ADD: (1X3)+(2X2)=7 (TENS-DIGIT ANSWER).
3. MULTIPLY THE TENS DIGITS: 1X2=2 (HUNDREDS-DIGIT ANSWER).
4. COMBINE: 276 (THE ANSWER).

THOUGHT PROCESS SUMMARY

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EX 2:

31 X 24 = ?

1. MULTIPLY THE ONES DIGITS: 1X4=4 (ONES DIGITS ANSWER).
2. CROSS-MULTIPLY AND ADD: (3X4)+(1X2)=14 (USE THE 4 AS THE TENS-DIGIT ANSWER, AND CARRY THE 1).
3. MULTIPLY THE TENS DIGITS, AND ADD THE 1: (3X2)+1=7 (HUNDREDS-DIGIT ANSWER).
4. COMBINE: 744 (THE ANSWER).

THOUGHT PROCESS SUMMARY