Question

without adding find the sum of following numbers. 1+3+5+7+9+11+13+15+17+19+21​

Answer 1

Answer:

121

Step-by-step explanation:

addition of odd nos in the sequence result into stepwise sqauring.

eg 1

1=1 square

1+3=4 (square of 2)

4+5= 9 (square of 3)

so 121 is 11th step.

so 11square =121

Answer 2

121

Step-by-step explanation:

simplify add 1+3+5+7+11+13+15+17+21=11. THAT MEANS AT HERE WE SEE ELEVEN UNITS. THEN. MULTIPLY THIS 11 WITH IT SELF GIVES 121. AND THAT IS A TRUE METHOD. WHICH I HAD BEEN READ IN MY SCHOOL.

BUT THIS METHOD IS ONLY VALID FOR ODD DIGITS.