We already know the applicability of the digital sum is very vast, as far as objective-based competitive exams are concerned, it can be applied in two ways:
1) At the start of Question i.e in question from number system, BODMAS, Algebra etc.
2) At the final calculation of Question i.e. in different topic of Aptitude like in work time wages, average etc.
- Do not try to apply the digital sum in almost every calculation as this may waste your valuable time in the exam. The method is good and can be applied in most of the calculations but at the same time, it may be hazardous if you try to apply everywhere. If the unit digit of options is different, the unit digit or last digit check method has an edge over the digit sum method.
1)The value of 7549 - 3468 - 5065 is
-984
The digit sum of
7549 → 7
3468 → 3
5065 → 7
thus 7549 - 3468 - 5065 → 7 - 3 - 7 → -3 or 6, hence the correct answer will have digit sum as 6 only option B matches i.e. -984, the digit sum of which is -3 or 6
2)The value of 7549 x 3468 x (-5065) is
-132601355580
The digit sum of
7549 → 7
3468 → 3
5065 → 7
thus 7549 x 3468 x (-5065) → 7 x 3 x (-7) → -3 or 6, hence the correct answer will have digit sum as 6 only option A matches i.e. -132601355580, the digit sum of which is -3 or 6
3)Of the given numbers, one number is a perfect square number which is it?
30276
4)Of the given numbers, one number is a perfect square number as well as a perfect cube no which is it?
117649
5)Find the value of \(7875 \times 4574 \times697 \over82\)
306172125
6)What will the value of the sum of Rs 537000 if it is increased by 10% then further increased by 17% and finally reduced by 10% ?
622007.1
7)The volume(in cm3) of a cone with radius of base 119 cm and height 207 cm is:
3070914
8)The value of \({3 \over 1.2}+{3 \over 0.12} + {3 \over 0.012}+ ....upto \space8\space terms..is\)
27777777.5
9)If a = 42 and b = 18, the value of a(a2 - 3a + 3) - b(b2 + 3b + 1) is
62100
10)The value of \({30.25 \% \space of \space 40200} \over 16.75 \% \space of \space 24200\)is
3
11)The price of an article increases by 6.25% every year. If the difference between its price at the end of the second and the first year is Rs. 531.25, then what will be its price (in Rs) at the start of the first year?
8000
12)A certain sum amounts to Rs. 13754 at 15% p.a. in \({2}{ 4 \over 15 }\)years, interest compounded yearly. The sum is:
Rs.10000
13)The average monthly expenditure of a family was Rs.18,600 during the first three months, Rs.21,750 during the next six months, and Rs.22,840 during the last three months of the year. If the total savings during the year was Rs.1,42,020, then the average monthly income (in Rs.) of the family was:
33070
14)A train is running at a speed of 99 km/h. If the train is 565 m long, then what will be the time (in seconds) taken by it to cross a 975 m long tunnel?
56
15)A shopkeeper allows 18% discount on the marked price of an article and still makes a profit of 25%. If he gains ₹106.6 on the sale of the article, then what is the marked price of the article?
Rs 650