1) Let the no. of dresses susan has be x
so Jane's no. of dresses is x+40
after susan gives jane 36 dresses,
susan --> x-36
jane --> x+40+36
--> x+76
since susan has 1/5 of jane's, you can form this equation,
(x-36)5 = x+76
5x - 180 = x+76
4x = 256
x = 64
jane --> x + 40
--> 64 + 40
--> 104 #
2) Mr Chen's age currently --> 36 +8 =44
5 years ago --> 44-5 = 39 #
3) 13 x 7 = 91 #
Note: I don't know the correct working, i think it has something
to do with factors.
4) Don't be affected by the large number. If you look carefully,
there is a pattern.
273 to the power of 120 means
273 X 273 X 273 ......... (120 times)
since the qn ask for last digit, just take the last digit to
multiply
3 X 3 X 3 X 3 .......(120 times)
You will see a pattern
3 X 3 = 9
9 X 3 = 27
27 X 3 = 81
81 X 3 = 243
243 X 3 = 729
729 X 3 = 2187
2187 X 3 = 6561
6561 X 3 = 19683
The pattern of the last digits
are, 3,9,7,1,3,9,7,1.......
So each group contains 3,9,7,1
there are 4 "things" in the group, so you take 120/4 = 30
30 is a whole number, which means the last digit is 1 #
IMPORTANT!!
In other cases, if they ask other numbers which you may not get
a whole number. You may get remainders, remainder of 1, 2, or 3
which corresponds to the last digit of 3,9,7 respectively. 1 is
when there are no remainders.
PSLE maths students do not learn expansion, equation and solve
for x lah.
PSLE maths students do not know what is the power of 120 lor and
question 4 What is the last digit of
273 to the power of 120? is not a real PSLE maths question
lor.
Some
months ago in homework forum, someone posted a maths question
that uses RELATIVE VELOCITY and claimed that it is a PSLE Maths
lor. LOL.
