Arithmetic Operations Questions and Answers

Answer: C

Sohail has to pay ₹ 100.50.

Add the cost of each item, taking the quantities into account:

\[ \begin{aligned} \text{Crayons} &= 15.50 \\ \text{Pencils} &= 2 \times 14.00 = 28.00 \\ \text{Sketch pens} &= 22.50 \\ \text{Scissors} &= 17.00 \\ \text{Glazed paper} &= 5 \times 2.50 = 12.50 \\ \text{Stickers} &= 5.00 \end{aligned} \]

\[ 15.50 + 28.00 + 22.50 + 17.00 + 12.50 + 5.00 = 100.50 \]

He buys no eraser, so its ₹ 2.00 is not included. Miscounting a quantity gives the distractors: one packet of pencils instead of two gives 86.50, and four sheets of glazed paper instead of five gives 98.00.

Answer: B

The total travel time is 29 hours 35 minutes.

Split the journey at midnights:

\[ \begin{aligned} \text{30 May, 23:40 to 24:00} &= 20\ \text{min} \\ \text{31 May, whole day} &= 24\ \text{h} \\ \text{1 June, 00:00 to 05:15} &= 5\ \text{h}\ 15\ \text{min} \end{aligned} \]

\[ \begin{aligned} \text{Total} &= 20\ \text{min} + 24\ \text{h} + 5\ \text{h}\ 15\ \text{min} \\ &= 29\ \text{h}\ 35\ \text{min} \end{aligned} \]

29 hours 15 minutes is what you get by forgetting the 20 minutes before midnight, and both 28-hour options fall more than an hour short of the true time.

Answer: C

7041 should be subtracted.

First find the sum, then the difference from 17863:

\[ \begin{aligned} 8008 + 8088 + 8808 &= 24904 \\ 24904 - 17863 &= 7041 \end{aligned} \]

Check: 17863 + 7041 = 24904. The option 7141 is off by 100, a typical slip when borrowing in the hundreds column; 6121 and 6131 fail the same check.

Answer: D

The mug holds 320 mL.

Fifty full mugs empty the 16-litre bucket, so one mug holds one-fiftieth of 16 litres. Convert to millilitres first:

\[ \begin{aligned} 16\ \text{L} &= 16000\ \text{mL} \\ 16000 \div 50 &= 320\ \text{mL} \end{aligned} \]

Check: 50 × 320 = 16000 mL. The other capacities are too small: 50 mugs of 250 mL hold only 12.5 litres, 50 of 275 mL hold 13.75 litres, and 50 of 225 mL hold 11.25 litres.

Answer: C

The railway station is 15 km from her home.

The first 2 km cost ₹ 50 together. The rest of the fare pays for the extra kilometres at ₹ 16 each:

\[ \begin{aligned} 258 - 50 &= 208 \\ 208 \div 16 &= 13\ \text{km} \\ 2 + 13 &= 15\ \text{km} \end{aligned} \]

The trap is stopping at 13 km, which counts only the kilometres after the first two. 12 km and 18 km do not fit: 12 km would cost 50 + 10 × 16 = ₹ 210, and 18 km would cost 50 + 16 × 16 = ₹ 306.

Answer: C

The number is 25.

The remainder is 5 and the divisor is twice the remainder, so the divisor is 10. The divisor is also 5 times the quotient, so the quotient is 2. Then use dividend = divisor × quotient + remainder:

\[ 10 \times 2 + 5 = 25 \]

Check: 25 ÷ 10 gives quotient 2 and remainder 5. 15 is divisor plus remainder; 52 and 48 do not leave remainder 5 when divided by 10.

Answer: B

One millimetre is the same as 0.1 cm.

\[ \begin{aligned} 1\ \text{cm} &= 10\ \text{mm} \\ 1\ \text{mm} &= \tfrac{1}{10}\ \text{cm} = 0.1\ \text{cm} \end{aligned} \]

In metres, 1 mm = 0.001 m, since 1 m = 1000 mm. So 0.01 cm is ten times too small, while 0.01 m (1 cm) and 0.1 m (10 cm) are ten and a hundred times too large.

Answer: D

The number to subtract is 2563.

\[ \begin{aligned} 9909 + 9099 + 9009 &= 28017 \\ 28017 - 25454 &= 2563 \end{aligned} \]

Check: 25454 + 2563 = 28017. The other options rearrange the same digits (2356, 2365, 2536) and fail this check.

Answer: B

The cheapest is 750 packets of ₹ 7.50 each.

\[ \begin{aligned} 75 \times 750 &= 56250 \\ 750 \times 7.50 &= 5625 \\ 90 \times 750 &= 67500 \\ 900 \times 7.50 &= 6750 \end{aligned} \]

Here 7.5 dozen is 90 items and 75 dozen is 900 items. The second option costs ₹ 5625, the least; 75 dozen at ₹ 7.50 (₹ 6750) is close but slightly more.

Answer: D

The cost is ₹ 57.

The first 50 g cost ₹ 15. The remaining 300 g make six further blocks of 50 g at ₹ 7 each:

\[ \begin{aligned} 350 - 50 &= 300\ \text{g} = 6 \times 50\ \text{g} \\ 15 + 6 \times 7 &= 15 + 42 = 57 \end{aligned} \]

₹ 42 is the additional charge alone, forgetting the first ₹ 15, and ₹ 50 counts only five additional blocks of 50 g.