GATE 2026 ES – Previous Year Questions with Solutions
All 65 questions of GATE 2026 ES with answers and explanations. Read each question, then practise it by topic or as a full paper.
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- Question 1 – Suresh said, “I did it yesterday.” Which option gives the correct indirect speech?
- Question 2 – Which tile continues the sequence shown? The graphical options A–D are included below the sequence.
- Question 3 – An art gallery’s walkways are shown as lines. Each black dot is a junction. A guard placed at a junction watches every walkway incident on it. Find…
- Question 4 – In a certain year,2 June is Thursday. What day is 3 July in that year?
- Question 5 – Six coins show heads H or tails T. The Starting Arrangement is H H H T T T and the Final Arrangement is T T T H H H, as illustrated. One step…
- Question 6 – Exacerbate : Mitigate :: . Choose the corresponding word pair.
- Question 7 – The paper net in Panel I is folded along its dashed lines into a cube, with shaded regions outside. Which displayed cubes in Panel II can result?
- Question 8 – In a population, every high-cholesterol patient also has high blood pressure (BP). Some high-BP patients have diabetes, but no patient has both high…
- Question 9 – Four people P, Q, R, S have distinct ages. P says “I am younger than S.” Q says “I am neither the youngest nor the oldest.” R says “P is older than…
- Question 10 – Three externally tangent circles C 1,C 2,C 3 have centers O 1,O 2,O 3 and radii r 1=2 cm,r 2=1 cm,r 3. The angle O 1O 3O 2 is 90,as shown. Find r 3 in…
- Question 11 – Find the matrix X satisfying 2X+pmatrix1&2\\3&4pmatrix=pmatrix3&8\\7&2pmatrix.
- Question 12 – Evaluate x/1+ x\,dx,where c is an integration constant.
- Question 13 – The global minimum of f(x)=3x4+4x3-12x2+6 for real x is
- Question 14 – One card is selected randomly from 26 cards bearing the English alphabet, one distinct letter per card. What is the probability that the letter is E…
- Question 15 – Which expression is Pearson’s chi-square statistic? Here O i,E i are observed and expected frequencies,n is the number of observations, O and are the…
- Question 16 – For the reversible elementary reaction A+B C+D,the forward and reverse rate constants are k f and k r. The equilibrium constant is
- Question 17 – Which enzyme class cleaves C–C, C–O or C–N bonds by elimination to form double bonds or rings, or catalyzes addition to double bonds?
- Question 18 – Malaria is caused by which type of microorganism?
- Question 19 – Consider: S1 Absolute pressure equals gauge pressure plus atmospheric pressure. S2 Gauge pressure uses absolute zero as datum. S3 Absolute pressure…
- Question 20 – Match processes P Activated sludge, Q Anaerobic filter, R Trickling filter, S Anaerobic digestion with (i) anaerobic suspended growth,(ii) anaerobic…
- Question 21 – In air pollution control device design, the size of particles removed with 50% efficiency is called
- Question 22 – Which is the general decreasing order of atmospheric gas abundance?
- Question 23 – Which is NOT part of proximate analysis of municipal solid waste?
- Question 24 – A species with an ecosystem impact disproportionately large relative to its population is called a species.
- Question 25 – Which principle is directly related to environmental compensation?
- Question 26 – How many Sustainable Development Goals are included in the UN General Assembly’s 2015 resolution “Transforming Our World: the 2030 Agenda for…
- Question 27 – Match ISO series P 14001,Q 14020,R 14040,S 14060 with the printed usages: (i) Environmental labeling,(ii) Evaluation of environmental management…
- Question 28 – Which reactions are related to tropospheric smog formation? Select all that apply.
- Question 29 – Which processes primarily remove organic matter in sludge? Select all that apply.
- Question 30 – Total Kjeldahl Nitrogen includes which forms of nitrogen? Select all that apply.
- Question 31 – Which statements are correct? Select all that apply.
- Question 32 – Which statements about global warming are correct? Select all that apply.
- Question 33 – Which are associated with life-cycle assessment? Select all that apply.
- Question 34 – A six-hour rainfall of 6 cm has a return period of 40 years at a station. Find the probability of a six-hour rainfall of this or greater magnitude at…
- Question 35 – A rectangular channel of width 5 m carries 15\,m3/s. For g=9.81\,m/s2,find the critical velocity in m/s, rounded to three decimal places.
- Question 36 – Classify the differential equation dy/dx+x2y=0.
- Question 37 – Find the eigenvalues of A=pmatrix2&2&3\\2&5&6\\3&4&10pmatrix.
- Question 38 – Which sequence correctly describes breakdown of DNA into lower-molecular-weight compounds?
- Question 39 – Match CPCB continuous ambient monitoring pollutants P SO 2 (µg/m³),Q NO 2 (µg/m³),R PM 2.5 (µg/m³),S CO (mg/m³) with methods (i)…
- Question 40 – Match stability P Strong instability, Q Neutral stability, R Surface inversion, S Aloft inversion with plume behavior (i) Fanning,(ii)…
- Question 41 – A water sample has Na+,Ca2+,Mg2+,Cl-,SO 42-,NO 3- concentrations 30,10,15,30,60,5 mg/L respectively. Atomic weights (g/mol) are Ca 40,Mg 24,Na 23,Cl…
- Question 42 – For AX=B,where A=pmatrix2&5\\5&-2pmatrix and B=pmatrix7\\3pmatrix,which statements are true? Select all that apply.
- Question 43 – Which statements about electron donors (ED) and acceptors (EA) in wastewater reactions are correct? Select all that apply.
- Question 44 – Which statements about reverse osmosis (RO) are true? Select all that apply.
- Question 45 – Which statements about coagulation–flocculation are true? Select all that apply.
- Question 46 – Which are assumptions of the Gaussian plume dispersion model? Select all that apply.
- Question 47 – Sound levels at urban locations A, B, C, D are 40,55,65,75 dBA. Find the average sound level in dBA, to two decimal places.
- Question 48 – PM concentrations at seven locations are 45,40,55,65,60,35,50 µg/m³. Find their standard deviation in µg/m³,to one decimal place.
- Question 49 – At 1 atm and 300 K, air contains 340 ppmv CO 2. Assuming ideal gases, find its concentration in mg/m³,to two decimals. Use molecular weight 44 g/mol…
- Question 50 – The elementary reaction A B follows first-order kinetics with k=.01\,min-1. Find the batch time to reduce A from 100 M to 10 M, to one decimal place…
- Question 51 – For SO 2(aq) H++HSO 3- and HSO 3- H++SO 32-,the ideal equilibrium constants are K S1=1.310-2 M and K S2=6.610-8 M. At pH 4.0 and [SO 2(aq)]=1.0 M,…
- Question 52 – The figure calibrates absorbance against chromate concentration (CrO 42-,mg/L). For sample absorbance .35,find Cr(VI) concentration in mg/L, to two…
- Question 53 – A batch culture starts with 2 cells. Its first hour is a lag phase without multiplication; subsequently the cells grow exponentially with a one-hour…
- Question 54 – At a fixed temperature, a thermal treatment gives a 2-log₁₀ reduction of non-thermotolerant pathogenic microorganisms in 20 minutes. Under the same…
- Question 55 – A cylindrical roller gate of diameter 6.0 m and length 10.0 m sits on a dam as shown. Water is about to spill over the gate. Find the resultant water…
- Question 56 – A 100-minute rainfall event has cumulative rainfall (cm) 0,.5,1.2,2.6,3.3,3.5 at times (min) 0,20,40,60,80,100. Initial loss is .6 cm and the -index…
- Question 57 – An unconfined aquifer has an initial head of 25 m. After long-term pumping at .05\,m3/s,drawdowns are 3 m at radius 50 m and 1.2 m at radius 150 m.…
- Question 58 – An activated-sludge plant has influent flow .150\,m3/s,soluble influent and effluent BOD 5 of 84 and 11 mg/L, mean cell residence time 5 days, yield…
- Question 59 – A steady CSTR receives 300 L/hour with substrate concentration 150 mg/L. Required treatment efficiency is 76%. Substrate decay is half-order with…
- Question 60 – At height 30 m, a stack cross-section is divided into four equal sectors. Sector velocities are 15,17,19,21 m/s and corresponding SO 2 concentrations…
- Question 61 – An anaerobic system treats OFMSW with moisture content 20%,volatile solids (VS) 90% of dry solids, and biodegradable VS (BVS) 70% of VS.…
- Question 62 – Leaves have 50% moisture,.7% dry-basis nitrogen and C/N=50. Sludge has 75% moisture,5.6% dry-basis nitrogen and C/N=6.3. Find kg sludge/kg leaves to…
- Question 63 – Chemical A has ambient concentration 50 µg/m³ and a threshold-effect dose of 5 mg. Assuming an average breathing rate of 4 L/min and uptake of the…
- Question 64 – Find the first-quadrant area bounded by y=8-x and the coordinate axes, in integer square units.
- Question 65 – Land yields 7000 L bioethanol/hectare with energy content 21 MJ/L, replacing fossil petrol. Bioethanol and petrol footprints are respectively 10 and…