Without actually calculating, how much greater is the product of 98times 50 than the product 97 times 50

Its greater by 80. because 50 times 97 is one 50 less than 98 times 50. All multiplication is is adding a number by itself multiple times. for example 50 times 2 is 50+50 so knowing this you can tell that 50 times 97 and 50 times 98 differ by 50