Using four sevens (7) and a one (1) create the number 100. Except for the five numerals, you can use the usual mathematical operations (+, -, x, :), root and brackets ()
Pronounced as one letter,
And written with three,
Two letters there are,
And two only in me.
I am double, I am single,
I am black blue and grey,
I am read from both ends,
And the same either way.
I am a word that begins with the letter “i.†If you add the letter “a†to me, I become a new word with a different meaning, but that sounds exactly the same. What word am I?