Question set B — the calculation inside an NGN item
Three unbranded response-furniture specimens across a band: a drop-down chip shown closed and open with a highlighted selection bar, a four-row matrix grid with empty checkboxes, and a trend strip of three time-stamped cards joined by arrows.
Item 1 · Drop-down
A pump-delivered order for 1000 mL of lactated Ringer's over 10 hours is started at 2200.
Complete the sentence: "The nurse sets the pump at [ ] mL/hr and documents an anticipated completion time of [ ]."
Options, first blank: 83 · 100 · 125 · 167 Options, second blank: 0600 · 0700 · 0800 · 1000
Rationale. 1000 mL ÷ 10 hr = 100 mL/hr. Ten hours after 2200 crosses midnight: two hours reaches 0000, eight more reaches 0800. The clock arithmetic across midnight is what the item is actually testing.
Item 2 · Matrix
A child weighs 10 kg. The reference dose for the prescribed drug is 10 to 15 mg/kg/dose. Classify each prescribed dose as safe or unsafe.
| Prescribed dose | Safe | Unsafe |
|---|---|---|
| 90 mg | X — below range | |
| 120 mg | X | |
| 160 mg | X — above range | |
| 100 mg | X — at the lower boundary |
Rationale. Convert the range into this child's milligrams once: 10 kg × 10 mg/kg = 100 mg low, 10 kg × 15 mg/kg = 150 mg high. Then compare four times against 100 to 150 mg. A dose sitting exactly on the boundary is inside the range, not outside it.
Item 3 · Trend
A heparin bag of 25,000 units in 250 mL runs on a 70 kg patient at a protocol rate of 18 units/kg/hr.
Fill in each blank as the trend advances.
- 0800, initiation. Concentration: 25,000 units ÷ 250 mL = 100 units/mL. Rate: 70 kg × 18 units/kg/hr = 1260 units/hr. 1260 units/hr × (1 mL / 100 units) = 12.6 mL/hr
- 1400, result returns below band. Protocol adds 2 units/kg/hr: 70 kg × 2 = 140 units/hr more, giving 1400 units/hr. 1400 units/hr × (1 mL / 100 units) = 14 mL/hr
Rationale. The concentration never changes, so a titration is one multiplication and one division, repeated. Recompute from the concentration every time rather than adjusting the previous rate by eye.
Item 4 · Fill in the blank
An adult is 165 cm tall and weighs 70 kg. Using Mosteller, calculate the body surface area in square meters, then calculate the dose of an agent ordered at 100 mg/m².
Body surface area: ______ m² Dose: ______ mg
(165 × 70) ÷ 3600 = 11550 ÷ 3600 = 3.2083. Square root of 3.2083 = 1.79 m² 1.79 m² × 100 mg/m² = 179 mg
Rationale. Round the surface area to hundredths before multiplying, and round only once. Carrying the unrounded root through and rounding at the end shifts the dose.
Margin notenew wrapper, same arithmetic. Find the number and the item collapses. → BOOK 02 · P4
Takeawaythe NGN item types change what you click, not what you compute.