Easy but, Hard?

using bodmas (braket of division multiplication addition substraction) first multiply 689*367 then subtract 57 from that product we get 252809 here 9 is in units place.

By multiplying 9 of 689 with 7 of 367 expected unit digit will be 3,while subtracting 4 of 54 left over digit will be 9 Ans.

K.K.GARG,India

i used the BODMAS and solved the question

XXXX3-4=9

no solution

To the modulus 10: 9*7-4=3-4=9. With congruencies, which I don't know how to type.

Let's take a simple approach:

The last digit of $9\times 7$ is $3$ . The last digit of $3-4$ is $9$ , due to the fact that the quantity $689$ is positive.

Thus, the last digit of the value of the expression is equal to $9$ .

9x7=63....last digit is 3 ....using it to minus 4 unit digit in 54 is impossible, so you need to borrow 10 which means 10+3-4=9

There is no need to use BODMAS. Just multiply the unit place digits i.e 9 and 7 = 63 therefore , the units digit of the product will be 3. Now if we have to subtract 4 ( units digit of 54 ) from the product. We will use the simple carry-over property, therefore the unit's digit will be 13-4 = 9

Since the question is only searching for the unit digit, we can just use the numbers in the unit position (9, 7, and 4, in that order) thus 9 * 7 = 63, then 63 - 4 = 9. Simple as that.