it's more than 3600, so its greater than 60. it's less than 4900, so its less than 70. a no.'s root can end with six if the no. ends with 4 or 6. so the no is either 64 or 66. Now if it's 66, the square must be greater than sq of 65. 65 sq= 4225 the given no. is greater than sq of 65. Therefore the number is 66.
