Multiplication Tricks
25 x 33
825
33 divided by 4 =8r1
1 x 25 =25
so 825 is the answer
7/12 + 3/12
5/6
round to the tens place
568.9279
570
57,203 divided by 9
8
add up all digits
keep doing so until you only have one digit
that is your remainder, unless it is 9. if that happens the remainder is 0
Perimeter of rectangle with sides 4ft and 6ft
20 ft
CMXXXIX converts to what Arabic number
939
50 x 207
10350
207 divided by 2 = 103 r1
1 x 50 = 50
10350
4/25 divided by 4
1/25
4/100
round to the nearest ten thousandths place 56701.86287
56701.8639
34,783 divided by 5
3
look at the last digit
0 to 4 = remainder is that digit
5 = remainder is 0
6-9 = remainder is subtract it from 5 and then that is the remainder
What is the area of a triangle with a base of 5inch and a height of 3 inches
7.5 inches
LXXXVIII converts to what Arabic number?
88
75 x 23
1725
The trick is for multiplying by 75
23 x 3 =69
69 divided by 4 =17r1
add 25 to the end of the quotient
1725
4/5 equals what percent?
80
What digit is in the hundredths place
7846.827
2
76437 divided by 2
1
if the number is even, remainder is 0
if the number is odd, remainder is 1
What is the semi-perimeter of a triangle with sides 10in, 12 in and 14 inch
Semi Perimeter = 18in
CMXXXVll converts to what Arabic number?
937
415 x 11
4565
write down last digit
add last digit to digit left of it, regroup if needed (5+1)
move to the left (1+4)
move to the left (4+0)
1 1/4 days equals how many hours
30
8x102+3x101+2x10-1
830.02
27403 divided by 4
3
Use the last two digits
Divide those by 4 - 93 divided by 4 = 23 r1
The remainder of that is the remainder for the whole number
What is the area of a triangle with a hypotenuse of 5inch and leg of 4 inches.
6 (double check me on this one)
34
3061 x 12
36732
double the ones place and write it down
then double the next digit and add to the previous digit.
6 x2 + 1 = 13, write the 3 and keep the 1 for the next part
0x2+6=6 and then add the regrouped 1 = 7
regroup as needed
3x2+0=6
0x2=3=3
add a zero -furthest left
.15 = what common fraction
3/20
You can memorize common fractions or you can convert them
15/100 simplifies to 3/20
What number is represented in expanded notation
6 x 103 + 4 x 102 + 2 x 100 + 5 x 10-3
6402.005
45382 divided by 3
1
Add all of the digits
4+5+3+8+2=22
22 divided by 3 is 7 with a remainder of 1
What is the perimeter of a rhombus whose side is 16 1/4 inches
65 inches
DCCCLXXV + 125 equals what (answer in Arabic digits)
1000