Guides
Straight explanations of the NCERT topics that carry the most marks. Every worked example on these pages is calculated by the same deterministic engine that checks your answers inside Bolo — so the numbers here cannot drift away from the numbers in the app.
How do you use the lens formula to find the image distance?
NCERT Class 10 Science — Chapter 9, Light: Reflection and Refraction
The lens formula is 1/v − 1/u = 1/f, where u is the object distance, v the image distance and f the focal length. Rearrange it to 1/v = 1/f + 1/u, substitute with signs from the Cartesian convention, then take the reciprocal. The sign of v tells you whether the image is real or virtual.
Read the guide →How do you find the current in a series and a parallel circuit?
NCERT Class 10 Science — Chapter 11, Electricity
Combine the resistors into a single equivalent resistance first, then apply Ohm's law, I = V/R. In series, resistances simply add: R = R₁ + R₂. In parallel, the reciprocals add: 1/R = 1/R₁ + 1/R₂, which always gives a resistance smaller than the smallest individual resistor.
Read the guide →How do you balance a chemical equation step by step?
NCERT Class 10 Science — Chapter 1, Chemical Reactions and Equations
Count the atoms of each element on both sides, then adjust the coefficients in front of the formulas until every count matches. Never change a subscript: that rewrites the substance itself. Balance the element appearing in the fewest compounds first, and leave hydrogen and oxygen until last.
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Practise it, don’t just read it
Reading a worked solution is the easy half. Bolo has 16 interactive labs where you move the object, change the resistor or set the coefficient yourself, and a deterministic engine checks every step — free, with no account needed to start.
Open the labs →