FIFTH GRADE /SUBTRACTION / TEST 1.2
First is certainly incorrect ... .
The equation means 6xA - 25 = 119 .
nth triangular number is the sum of numbers from 1 to n. 20th is 20x21/2 = 210 olur. 15th is 15x16/2 = 120 .
Since nth triangular number is the sum of numbers from 1 to n, the difference is 20+19+18+17+16 = ...
99-50 is an example. So is 59-10 . 58-9 is not because 9 is not a 2-digit number.
Subtraction is defined also for negative integers and numbers .
Please have a look at ry1.
The difference of ages does not change .
Suppose we subtract another 25 from it, we get 0 because 25+25 = 50, 50+50=100, 100+100 =200 etc.
Write them under each other, you will soon see that B = 3 or 2 .
This is easier than the previous one. B should be 2 and ...
The 2nd paranthesis is equal to 0 .
ry1 gives the solution .
208 is nearly 225 which is the square of the 15 . So try numbers in the neighborhood of 15.
Think as if the figure is a rectangle; the perimeters are the same .
If a negative number in a negative paranthesis is not treated as a positive number, we lose consistency .
Let the smaller be 1, the second can not be integer. Try the smaller equals 2, the bigger should be 5, the couple does not satisfy the second
Let the larger be A and smaller B. 2xA = 5xB and 2x(A-B)=12 i.e. A=B+6 . Putting B+6 in the first gives 2xB + 12 = 5xB i.e. B=4
1275 + 225 = ?.